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Minor League Statistics Context
The trouble with writing about prospects is that while fans enjoy looking at stats they know and understand, Minor League stats do not provide the same insights that MLB stats can share. First and foremost, given player assignments from the player development department, there are aspects of a prospect’s performance that escape statistics and therefore must be quantified via scouting reports that highlight physical traits and approaches. If a prospect is working on a particular aspect of their game, their statistics may not necessarily reflect their value. Furthermore, each player’s age, assignment, and other contextual factors impact the judgment of their performance. Batting .275 does not carry the same weight in the Pacific Coast League as the Florida Southern League, nor does it carry the same weight for, say, a 23 year old AA prospect as it might for a 20 year old AA prospect.

Since this installment of this feature will focus on several batters, I have outlined the number of “regular” players in each minor league from Milwaukee’s A to AAA affiliates, and I have also shown the progression in “opposing difficulty.” Since BaseballProspectus showcases the opposingOPS and opposingTAv for minor league players, one can add to the context of their performances by understanding the difficulty of their competition (via opposing OPS, or OPS allowed by the pitchers each batter faced).

The goal of this chart is to serve as a backdrop for reading BaseballProspectus minor league statistics, and to add contextual information that can round out a player’s age, developmental profile, assignment, and scouting reports. One can dig into each Brewers prospect’s BaseballProspectus player page, or leaguewide minor league stats, and understand the range of competition for each player (which adds context to their performance).

Three Up
Jacob Nottingham, AA Biloxi (James Fisher): There is an argument to be made that Jacob Nottingham could rise to become the top positional prospect in Milwaukee’s system by providing above average power from behind the plate. While the main calling card is Nottingham’s power, the 21 year old catching prospect is improving his defensive game during his first career pass through AA. James noted that Nottingham “has really transformed his defensive game into a near average package. [Nottingham] really put in the time and has dedicated himself to the defensive side of the ball.” This observation echoes previous BaseballProspectus reports highlighting Nottingham’s athleticism on the defensive end of the game. Even if one is ready to criticize Nottingham’s batting line of .245 / .309 / .355, his .251 TAv matches the average Southern League catcher, and he has faced average competition for Southern League regulars.

Brett Phillips, AA Biloxi (Kyle Lesniewski): If Nottingham does not emerge as the system’s most valuable positional prospect, chances are Brett Phillips had something to say about it. The potential five tool centerfielder has really gone after his in-game power during his second pass at AA Biloxi. Phillips smacked 10 homerless extra base hits for the 2015 Shuckers in 98 PA; now, he can claim 30 extra base hits in 320 PA, including 11 home runs. One might wonder whether Phillips’s plate approach is an outgrowth (or cause) of the home run surge, as a previous moderate strike out (19 percent) / moderate walk (8 percent) profile in Advanced A has morphed into a high walk (11 percent) / high strike out (32 percent) approach with AA Biloxi. This is not necessarily problematic, as one might look for Phillips to morph his power-hungry approach and previous moderate contact approach as he becomes a more seasoned hitter (he remains young for AA at 22 years old). Notably, Phillips has faced slightly below average competition, but his .281 TAv trails only Garrett Cooper among Shuckers starters.

BaseballProspectus edged Phillips into their midseason Top 50 list, ranking the centerfield prospect at #49.

Jake Gatewood, A Wisconsin (Nicholas Zettel): Rummaging through game logs last year, Jake Gatewood caught my eye during his second stint at Rookie Helena (following a multi-level, Wisconsin / Helena double header on July 13, 2015). Gatewood’s power showed up in a big way: the infield prospect smacked six extra base hits in his first 10 games back at Helena, en route to a .292 / .361 / .523 performance over 147 PA (which included a massive plate discipline shift, to 34 K / 13 BB). James Fisher scouted Gatewood at A Wisconsin earlier this spring, noting that “much of his improvement has come this year from an adjustment in his starting position. He has lowered his hands slightly and that has led to a much shorter and direct path to the ball. While his plate discipline is still suspect, he has been making harder and more consistent contact.” Playing at third base, Gatewood slumped during June, but has turned another corner in July, posting five extra base hits and five walks in 47 PA thus far. Fans inclined to give up on Gatewood should consider his position change and mechanical adjustment during his age 20 season, and keep in mind that the power prospect is a work in progress that is also making progress.

Three Down
Ariel Pena, AAA Colorado Springs (James Fisher): In a season thin with silver linings, Ariel Pena emerged as late value from the 2012 Zack Greinke trade. Pena performed well in a brief swingman role, leading one to question whether the rookie would be able to further establish a big league niche for himself during the rebuilding campaign. Unfortunately, Pena has been hit hard all year, including a 22 K / 21 BB / 6 HR / 23 R stretch as a reliever for the Sky Sox. Pena is currently on the seven-day DL.

Monte Harrison, A Wisconsin (Kyle Lesniewski): Some Brewers fans questioned whether Gatewood and Monte Harrison would ever be separated by Brewers fans, given their adjacent draft rounds in the 2014 draft, and the fact that both players signaled a sea change for previous Scouting Director Bruce Seid. While Gatewood turned a corner with his major tool in 2016, the athletic and prime positioned Harrison also was burning up A Wisconsin before breaking his ankle. Fans can only dream on his .321 / .377 / .679 June, as one must question how this injury will impact his player development outlook for 2017.

Karsen Lindell, R Helena (Nicholas Zettel): Perhaps my rating of Karsen Lindell is my own fault, given that my main opinion of Lindell entering the season was formed on a collage of scouting reports, YouTube, and K / BB / HR and GB:FB numbers in Arizona Rookie ball. When there is little information on a depth prospect, or extremely young prospect, I often fall back on strike zone numbers and groundball numbers as a way to “paint” that pitcher’s approach. From an intriguing 29 K / 13 BB / 3 HR mark (and 51 percent groundball rate) against 147 batters in 2015, thus far Lindell is posting 5 K / 11 BB and 41 percent groundball rates in Helena Rookie ball. We must wait for the reports to see what Lindell has been working on, but thus far this sleeper pick looks premature on my part.

Pena, though, appears near the top of a very interesting leaderboard. Of all starting pitchers who threw at least 200 pitches in 2015, Pena ranks fifth in whiffs per swing. He induced more misses than such luminaries as Jose Fernandez, Jacob DeGrom, and Madison Bumgarner (among others). Somehow, the only pitchers with better whiff rates than Pena were Francisco Liriano, Clayton Kershaw, Chris Sale, and Max Scherzer.

This obviously is not to suggest that Pena is a huge breakout candidate; he’s always struck out a decent number of people, and his actual strikeout rate in the majors in 2015 was not absurdly high. In fact, at 8.9 per nine innings, it was right in line with his minor league averages. This, then, presents a puzzle: How does one get that many swings-and-misses and not post an elite strikeout rate?

An obvious possible answer (and definite truth) is that Pena has no idea where the ball is going. His minor-league walk rates (and 4.6 walks per nine in the big leagues last year) certainly indicate that he can’t throw strikes consistently, but that is not really a surprise. Minor League Baseball is littered with hard-throwing righties who couldn’t hit the broad side of a barn; most of those, however, don’t show up at the top of a whiff-rate leaderboard.

A second contributing factor is that this whiff rate may be mere variation and not truly representative of a specific talent that he has. However, without further data from minor-league parks (which does not exist), we have no way of directly proving or disproving this. I will therefore continue with tempered expectations, although it is worth noting that such a single-season whiff rate is spectacular even were it to eventually prove to be an outlier.

Francisco Liriano provides an interesting contrast. As he is an actual good major-league pitcher, there may not be any insight we can (or should) glean from a comparison of the two. However, Liriano’s walk rate makes him an interesting foil for Pena. Liriano appears at the top of the aforementioned whiff-rate leaderboard, but he also walks a ton of batters. He has obviously been a lot more successful than has Pena, but some of their characteristics are the same.

Similarly to Liriano, Pena doesn’t have good command of the strike zone but gets a ton of swings-and-misses. Unlike Liriano, though, Pena has had very little major-league success.

A quick glance at Pena’s pitch usage explains why. Where Liriano frequently shows off his changeup, Pena does not really have one. In his short big-league stint in 2015, he threw his changeup just over five percent of the time. Liriano, meanwhile, has thrown his nearly twenty percent of the time over the course of his career.

In many ways, none of this is that surprising. We all mostly knew that Pena was a hard thrower who had some good qualities but more bad ones. He appears destined for the middle of a bullpen somewhere, although his whiff rate could very well prove more important in one-inning stints than it has in longer outings and push him towards the end of games. Ultimately, if he ends up as a set-up man or closer (whether it be in Milwaukee or elsewhere), the inevitably low cost it would have taken to acquire him will make him a good value.

Maybe that is the lesson here, though. Pena is a mediocre starter with (apparently) one incredible skill. His lack of a changeup and subsequent inability to properly sequence his pitches has mostly mitigated his whiff rate. However, we have seen many average-at-best starters move to the bullpen and see immediate, relatively unexplainable success. Perhaps this is a key to Pena’s future: As a reliever, his lack of a changeup is less of an impediment to success. With less of a need to worry about sequencing, his whiff rate could spike, leading to a rise in strikeout rate and, ultimately, success.

That is obviously a bit of optimism and a look at his best-case scenario. However, the fact that his whiff rate ranked fifth among all starters is truly incredible, and it is worth taking note of. Seeing him figure out how to properly utilize such a skill were he to be moved to the bullpen would not be too much of a shock.

Stuff

We saw earlier that Nelson took the cake in terms of velocity, while Pena’s movement paced the team. On the other end of the spectrum, there was no such divide — one pitch had both the lowest velocity z-score and the lowest total movement z-score:

For a curveball, below-average vertical movement isn’t necessarily a bad thing, since the average such pitch already moves negative. Indeed, the fact that Fiers led all starters in curveball drop last season would seem to work in his favor.

Of course, all the dive in the world won’t count for anything if the pitch has no velocity. Only Jered Weaver, Mark Buehrle, and Julio Teheran threw their curveballs slower in 2015, and it showed. Fiers’s curve went for strikes just 43.0 percent of the time in Milwaukee, and when he put it in the zone, hitters such as Tyler Moore made him pay:

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Those kinds of dingers made Fiers’s curve worth -1.61 runs below average on a rate basis. The Brewers will miss Fiers overall in 2016, but I for one am glad that his curveball will stay with the Astros.

Run Values

Interestingly enough, though, Fiers’s curve didn’t finish last when it came to Linear Weights. Another starter, who remains on the team, held that distinction:

Peralta’s 2015 regression fell squarely on the shoulders of his sinker, which traveled nearly a mile and a half slower than it did in 2014. That meant the pitch often resulted in this sort of treatment, courtesy here of Curtis Granderson:

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But a run value alone doesn’t really do Peralta justice. For his case, we’ll look at something else.

TAv

Using the same samples from the velocity and whiff rate z-scores, I found the average and standard deviation for each pitch’s resulting TAv. These created TAv z-scores, to better reflect how hard batters hit an offering. They certainly clobbered Peralta’s heater:

How bad was this? The next-worst pitch, Tyler Cravy’s four-seamer, had a TAv 1.75 standard deviations over the mean. Only Vidal Nuno and Sean O’Sullivan allowed opponents to abuse them more than this. Let’s throw in another GIF of this atrocity, for good measure:

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I discussed Peralta’s meltdown in December, noting that the movement of his pitches actually improved in 2015. Let’s hope for his sake that he regains his velocity, because if he doesn’t, the 2016 campaign will bring more of the same kind of pain.

Whiffs

When it comes to swinging strikes, things get complicated. Unlike Fiers’s curveball and Peralta’s four-seamer, this pitch actually held its own in 2015:

Blazek didn’t earn many whiffs with the curveball, yet it still gave him 1.99 runs above an average pitch (per 100 appearances). That’s because it accrued its strikes a different way:

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Matt Carpenter and his fellow batters took the curveball for a called strike 30.7 percent of the time, an incredible amount. An exercise like this has limits, as Blazek demonstrates — no one metric can really capture all the value of a pitch.

That isn’t to say, however, that Peralta’s four-seamer didn’t struggle, or that Fiers performed well with his curveball. We can pretty conclusively deem one of those two the worst Brewers pitch of 2015. Hopefully, 2016 will bring more pitches like the ones we saw on Thursday (although, if the team continues this rebuild, we won’t witness great pitching for a few years).

Click here for a complete spreadsheet of all 39 pitches.

Beyond that, pitchers make a better target for sabermetricians, as we can quantify so many elements of their game. Thanks to PITCHf/x, we can now look at pitch usage, velocity, movement, release points, locations — and, most importantly, individual result breakdowns for each offering. This can lead us down any number of analytic rabbit holes, which is where our story begins.

Because we still have a few weeks until baseball returns, I’ve decided to pass the time by constructing arbitrary “best-of” lists. Most of them wouldn’t appeal to any sane person, but I feel that many fans of the Brew Crew would like to know the answer to this question. Of the many pitches we had the pleasure of viewing last season, which stood out above the rest? A question that broad doesn’t have one right answer, but it’s an entertaining exercise regardless.

To accomplish it, I looked at pitches that appeared at least 200 times, isolating myself to those that occurred when the player was in Milwaukee. (In other words, this won’t include Mike Fiers’s time in Houston or Jonathan Broxton’s work for St. Louis.) This gave me a sample of 39 pitches to work with:

Whose quiver contained the deadliest arrow? Well, we can look at the issue a few different ways, each of which has its own merit. I’ll run through them all, with fun GIFs and full explanations, then return with a final summary.

Stuff

When evaluating the quality of a pitcher, we can focus, broadly speaking, on two things: the process (think cFIP) or the results (think DRA). The same general logic applies to the pitches themselves. We’ll begin with a few metrics that will tell us how well the pitches theoretically should have performed in 2015; from there, we’ll then move to the measures of how well they actually performed.

For a pitch to blow away the opponent, it generally has to have either velocity or movement. We’ll thus begin our journey with these two categories. For this, I used the BP PITCHf/x leaderboards to find pitchers (separating starters and relievers) with 200 of each pitch type in 2015. I then found the average and standard deviations of each sample, from which I constructed velocity, horizontal movement, and vertical movement z-scores for all 39 offerings.

The pitch with the most power behind it might seem familiar:

Nelson’s curveball, which ranked above Sonny Gray and Jacob deGrom in terms of velocity, left hitters such as Aramis Ramirez guessing:

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For movement, I took the sum of vertical and horizontal z-scores, to get a rough measure of overall bite. Although the top offering here might not be your first guess, it certainly deserved its spot:

Pena’s four-seam fastball didn’t have much heat, but man, could it dance. Watch how it rises and tails away from Kyle Schwarber:

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Nelson saw more action than Pena did in 2015, which may explain why his curveball feels more familiar. Still, each of these offerings stood out in its own regard. As the Brewers experiment with their rotation in 2016, we’ll probably see a lot more of both the heater and the curve.

Run Values

With that said, velocity and movement alone don’t make a pitch. A better line of thinking would look at the actual production of a pitch, and for that, we have a unique metric.

Pitch Type Linear Weights measure the count changes by each pitch, as well as the result when the offering ends a plate appearance, and expresses it as runs above or below average. This metric generally achieves its goal, and its selection for top Brewers pitch (on a per-100 pitch scale) probably wouldn’t get too much blowback:

Rodriguez won this contest by a wide margin — Michael Blazek’s curveball came in second, at 1.99 runs above average. Darin Ruf would probably agree with that verdict:

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This shouldn’t come as a surprise, since Rodriguez’s cambio made his 2015 resurrection possible. In fact, the changeup was worth more (by this metric) on a rate basis than any other pitch, of any kind, in all of baseball. Taking note of that a few months back, Mark Simon crowned it the best pitch in the majors. Sadly, K-Rod will pitch in Detroit this season, so this changeup will no longer work in Milwaukee’s favor.

Whiff rate

But we shouldn’t stop there, because Linear Weights aren’t perfect. Aside from the fact that they don’t necessarily reflect true talent (which we’ll discuss in due time), they treat all changes of count the same way. In the eyes of Linear Weights, a swinging strike to begin an at-bat is the same as a foul ball, since each puts the pitcher ahead 0-1. That doesn’t testify to the quality of the offering, though — whiffs are clearly better than fouls, meaning the best pitches will usually maximize the former.

For that reason, we’ll move to swinging-strike rate. Here, it’s important to take into account the different baselines, as each pitch fools hitters to different extents. To level the playing field, I created some more z-scores, using the averages and standard deviations of the whiff rates from the aforementioned velocity samples. As with the Linear Weights, the winner here won’t shock anyone:

Here, too, the leader dominated the competition: The runner-up — Neal Cott’s cutter and its 15.7 percent whiff rate— only topped the mean by 1.24 standard deviations. Based on this hilarious A.J. Pierzynski swing, I can’t argue with that:

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I covered Smith’s transcendent slider back in June, and although Smith himself faded a bit down the stretch, this pitch didn’t miss a beat. Unlike Rodriguez, Smith should stick around, so this glorious breaking ball will continue dominating for the Brewers.

In the end, Nelson’s curveball, Pena’s four-seamer, Rodriguez’s changeup, and Smith’s slider disrupted plenty of hitters last year. These standout offerings gave us something to look forward to in an otherwise dismal campaign. (On that note: Later in the week, I’ll use this methodology to find the worst Brewers pitches of the 2015 season. Until then, we’ll simply have these masterpieces to keep us warm.)

Enter Ariel Pena. He came to the Brewers three years ago in the Zack Greinke trade and, until about a month ago, had remained in their farm system ever since. That changed after a rainy series in Cincinnati, which depleted the team’s depth and forced it to dig into the minors. Pena came up, received an opportunity to start, and did well enough to see a few more turns through the rotation.

The right-hander has made four total starts in 2015, in which he’s held his own, allowing eight runs in twenty innings for a 3.60 ERA. His 3.86 overall DRA, while not exceptional, certainly tops the unsightly marks that his rotation comrades have posted. There’s the potential here for a satisfactory starting pitcher in 2016 and beyond; however, he’ll need to improve some things for that to happen.

Of the three pitches in Pena’s arsenal — a four-seam fastball, a changeup, and a slider — the latter clearly reigns supreme. The slider has induced a whiff on 26.1 percent of its usages, has gone for a ground ball on 50.0 percent of its trips to the field, and overall possesses a .138 TAv against. Implementing this deadly offering for 33.1 percent of his pitches has certainly helped Pena achieve what he’s achieved.

Interestingly, Pena’s slider hasn’t stood out in terms of velocity or movement:

As opposed to, say, Smith’s slider — whose bite allows him to blow it past any kind of hitter — Pena’s has seemed to become dominant by contrasting with his fastball, which has run an incredible amount:

Pena has consistently placed the slider in the lower right of the zone; the four-seamer has gone there somewhat often, but Pena has kept its usage unpredictable, elevating the slider in the process.

While its results obviously trail those of the slider, the four-seamer hasn’t exactly failed Pena. Sure, he’d probably like a higher rate of strikes than the 59.4 percent clip it’s provided, but he can’t complain about 8.0 percent swinging strikes and 10.4 percent popups. Overall, the pitch gives him a solid offering to use 62.0 percent of the time; along with the slider, it makes for a pretty good 1-2 punch.

So what’s the issue here? Well, Pena’s third pitch — the changeup — hasn’t shown anything resembling competence in its brief trials. Appearing 4.9 percent of the time thus far, it’s put up a 55.0 percent strike rate and a 0.0 percent whiff rate. Most hurlers need to have at least three decent pitches to make the cut as a starter, and those numbers fall far short of that standard.

The changeup’s failure becomes more pertinent when we consider Pena’s platoon split. This season, he’s held right-handers down to a .202 TAv, but lefties have knocked him around to the tune of a .329 TAv. His disparate pitch mix against them accounts for most of that:

In general, sliders will have heavy platoon splits, while changeups can neutralize them. Pena, recognizing this, has essentially made the changeup a lefty-only pitch; the pitch’s aforementioned output tells you how well that plan has worked for him. If he wishes to stick as a starter, Pena will need something that can retire left-handed batters — meaning he’ll either have to better his changeup or experiment with another pitch, such as a more overhand curveball.

In the end, Pena clearly has the potential to remain in the show — any pitcher with a slider this phenomenal can’t stay in the minors for long. With that said, a sole elite offering does not a capable pitcher make. Pena must progress with his changeup to stay afloat, lest he become a lowly LOOGY. Pena may yet help the Brewers’ rotation return to respectability; it all depends on where he goes from here.