In 2017, the 84th best pitcher averaged approximately 10 runs prevented, establishing the 90th percentile performance point; in 2018, the 89th best pitcher averaged approximately 10 runs prevented, suggesting that the 90th percentile performance did not change. If you like false certainty, even here the decimal points look similar, as the 2018 cut-off was 10.221 average runs prevented versus 10.229 average runs prevented in 2017. Let’s call it 10 Average Runs Prevented for fun…

 Exploring Runs Prevented || Aces Do Not Exist || Rotation Spots || Third-Time Charmers

What is Runs Prevented? Runs Prevented is a relatively basic statistic that attempts to measure the quality of a pitcher’s performance within their run environment (which is roughly the combination of their ballpark, which can impact scoring, and their league, which can impact the mix of talent faced). Measuring pitching is difficult because unlike batting stats, you cannot simply “count up” with pitchers; a team that scores 750 runs is  likely better than a team that scores 700 runs, but a team that allows 650 runs is likely better than a team that allows 700 runs. So, assessing pitching in a “run environment” requires accounting for that “negative space” (in this example, between 650 RA and 700 RA). Throughout the 2018 season, I developed an Average Runs Prevented statistic that attempted to track variance in park factors (between Baseball Prospectus Pitching Park Factor and Baseball Reference Park Factors) as well as variance in league environments. Usually these differences did not amount to much, but tracking them is an important step to understanding variance and reflecting uncertainty in the Runs Prevented metric: I can say “Jeremy Jeffress prevented 24.63337 runs in 2018,” or I can say “on average Jeremy Jeffress prevented between 23 and 26 runs in 2018,” or I can say, “Jeffress prevented 25 runs.”

…The short lesson: if you’re an MLB pitcher that prevented 10 runs, you’re really, really good. This holds regardless of role. In 2018, the top ten percent of all MLB pitchers featured 53 starting pitchers and 36 relief pitchers, which is quite a swing in favor of starting pitching quality; in 2017, these 90th percentile pitchers featured 41 relievers and 43 starters. What’s important here is to takeaway that great relievers prevent enough runs to break into the top threshold of league performance; Runs Prevention need not categorically be dominated by starting pitching, which is one reason the Brewers did not need a starting pitcher at the trade deadline (thanks to their strong bullpen).

Aces are more difficult to define than “Average Runs Prevented.” I can at least give you a math equation for Average Runs Prevented at the end of the day. But an “ace” can be many things;

• Some fans want an ace to be a breathy “dude” or “guy”, a “stud” atop the rotation. File this one under the debate about playoff dudes,  “Do you want Jhoulys Chacin and Wade Miley to pitch in the playoffs?” (Yes, actually);

• Some people ascribe to a theory than an “ace” is simply the best pitcher on each MLB team (e.g., 30 teams means 30 aces, and no team can have more than one ace);

• Scouts like to define “aces” in very rigorous ways, focusing on the quality of a pitcher’s stuff (typically better than average fastball and off-speed or breaking ball is the minimum stuff requirement for acehood), as well as their command (must be great), and probably their frame, too (it’s good to project innings from an ace). But I take it that this is not how most fans mean “ace,” and it’s also no fun because aces rarely exist under this mold (#EveryoneIsAMidRotationStarter);

• Finally, there’s the simple stipulation that an “ace” is an elite starting pitcher, at the top of the league in terms of performance (presumably, hopefully, for multiple consecutive years. For example, this is why people say Clayton Kershaw is an ace, but Junior Guerra is not. I used to be sure of the importance of consistency, but….well, aces hardly exist under this requirement, either).

In this analysis, I am going to demonstrate two of the shortcomings with the idea of using performance to define the concept of an ace.

(1) Threshold of Greatness. Seeking the 90th percentile of MLB pitchers seems like a very high standard; it’s quite literally the top of the league, but includes a large enough group of pitchers to make meaningful comparisons. What I mean by this is, if we used a more strict threshold, there really would not be any aces; take the Top 10 pitchers by Runs Prevented in 2017 and 2018, for instance:

I rather like this, in the sense that it demonstrates that aces do not exist, but it doesn’t pass the eye test. If you’ve designed a threshold where only Corey Kluber, Chris Sale, and Max Scherzer are aces in 2017 and 2018, but not Kyle Freeland, Justin Verlander, Clayton Kershaw, Blake Snell, or Jacob deGrom, you’ve probably missed the threshold and poorly defined the concept.

An interesting problem arises with using the 90th percentile threshold, however: starting pitchers no longer dominate the proceedings, and 10 Average Runs Prevented is the measure for an ace. This surely won’t do for Brewers fans, for example, as 2016 Junior Guerra is absolutely, positively an ace under this regard; interestingly enough, so are 2018 Jeremy Jeffress, Josh Hader, and Wade Miley. Of course, this is conceptually interesting because Brewers fans absolutely did not want Miley to work in the rotation, and he was an “ace,” it turns out. Really, a truly fantastic pitcher, better than 90 percent of the MLB. Jeffress and Hader are difficult in terms of “acehood” because they do not start ballgames; but it’s not clear to me than an ace must start ballgames.

Consider the false controversy to open 2018, regarding whether or not Josh Hader should start or work in his relief role; as a starter, the concern is clearly that Hader does not have the command or pitching profile to work through a batting order multiple times, and based on news throughout the season, his delivery is probably too high effort to withstand a starting workload. But that was never the debate; the debate among angry fans was, “Josh Hader should start because the Brewers must see whether he can be an ace.” Ironically, based on the 90th percentile threshold of Runs Prevented, Hader is an ace, undoubtedly so (in fact, he’s better than 95 percent of the league in 2018; Jeffress was even better, beating 98 percent of the MLB). In this debate, it seems that the ideal of “finding an ace by making sure they can start games” misses the concept of what an ace ought to do (“consistently prevent runs at an elite level”), and so the Hader starting pitching controversy falls by the wayside.

Both Hader and Jeffress are aces, on this model. As they should be.

(2) Consistency. Josh Hader showed flashes of brilliance during the 2017 season, in which he established a clearly valuable MLB “floor” performance level, and raised debates about how high the “ceiling” performance could be. I gather this is in part why fans wanted so badly to see Hader start; when he began his career in the bullpen, it was certainly due to his tough season at Triple-A Colorado Springs, where he lost his breaking ball and had his stuff and command profile back-up a little bit. Yet Hader excelled in his MLB debut role, working through some command issues by offsetting bad outings with a dozen scoreless multi-inning appearances. Hader prevented between 13 and 14 runs in 47 and 2/3 innings.

Any team will receive considerable value from a pitcher that prevents more than 10 runs in a season; no team would balk at a chance at 90th percentile runs prevention production. Yet, there is more value to be had from pitchers that can repeat the feat in consecutive seasons. For example, 639 pitchers worked in both 2017 and 2018 seasons, with considerable variance in their production. The typical back-to-back pitcher in 2017 and 2018 found their runs prevented total shift by at least nine runs, with their innings pitched total fluctuating by 33. If you ascribe to the rule of thumb that approximately ten runs are equivalent to “one win” when balancing Runs Scored and Runs Allowed, the MLB pitchers that worked in 2017 and 2018 fluctuated enough to produce as many as 575 total wins (or losses), depending on how teams balanced their resources (as a side note, this is one reason organizations should not ever tank, and should always try to compete: there are always tons of runs that can be “captured” every year through trades, free agency, and player development fluctuations).

This is where I believe fans and analysts turn against “one year aces” like Junior Guerra. The idea is not that Guerra was not valuable to the Brewers in 2016, but that it is more valuable to have a pitcher that a team can “depend” on to produce 90th percentile performance year-in, and year-out. The trouble is, these pitchers do not readily exist. Looking at 2017 and 2018, here are the pitchers that were able to produce 10 Average Runs Prevented (or better) in both seasons:

This seems like a good list, for two reasons: (1) it’s intuitive enough to pass the “eye test” in terms of including pitchers like deGrom and Kershaw, but it also includes some “newcomer” aces like Aaron Nola; (2) it includes enough counterintuitive pitchers that we can look into new cases and further define quality pitching roles. Here, I’m thinking of Josh Hader (who is an ace in relief), JA Happ (who has morphed into an extremely consistent late career pitcher), and Dellin Betances (who is typically criticized as a middle reliever when it comes to contract negotiation matters, but should be thought of in the highest terms of consistency). Moreover, this table shows the benefit of being more inclusive in terms of defining aces, rather than less exclusive. Here’s what happens if you only consider pitchers with consecutive 20+ Runs Prevented seasons to be aces:

This list is visually appealing insofar as we all know that these pitchers are great, the top of the game in fact. This group would be the true 99th percentile of the game of baseball at the moment. But, it does not capture easily acquired pitchers (except for the Cleveland arms, perhaps, in Carlos Carrasco and Corey Kluber, this is an expensive group in terms of draft status, contract, or prospect resources required for acquisition). So, the cases of aces exclude most MLB teams from acquiring aces. Furthermore, there is no diversity of roles in this table, and to my eye that seems like the biggest shortcoming in this definition of the ace: for if we continue to define aces according to the highest possible standard, we will continue to replay and repeat the “Josh Hader should start” debate, and miss the reasons why Wade Miley or Jeremy Jeffress could be aces, too.

Building a pitching staff based around flexible roles, or based on elite relief roles and interchangeable starting rotation roles, does not preclude acehood. In fact, the 2018 Brewers demonstrate that effectively, both with multi-year consistent aces (Hader) and (potentially) one-off successes (Jeffress, Miley).

For a team that is seriously out performing their run differential (expected Runs Scored / Runs Allowed record), Hader more than any other pitcher personifies a bullpen that is ready to support their club in any scenario and (usually) bring home the win. Even failings in close games, such as Sunday’s 1-3 loss to the Twins, typically have the stamp of a poor offensive performance, leaving it difficult to fully blame the bullpen or pitching staff as a whole unit. Hader is also quite a thrilling personality, as he exemplifies one of the prospects acquired during the first rebuilding stint (started July 2015 by President Doug Melvin) reaching the MLB in a successful role. Now that Hader is a successful reliever, it’s tough for fans to remember that not even three years ago he was a questionable prospect that could offer many potential futures to the Brewers; now Hader represents a winning club on the field, which undoubtedly enhances his face of the post-rebuilding Brewers.

It’s tough to hang on a role on Hader right now. The southpaw is undoubtedly capable of serving as a closer, as well as a multi-inning fireman in any part of the game. He’s a true strategic role player for the Brewers, but even his elite performance is not enough for some fans; some Brewers fans and analysts continue to question whether Milwaukee should employ Hader as a starter, insinuating that even 27.3 IP, 1.10 DRA, 8 runs prevented (!) of relief work are not enough to settle the question of Hader’s role.

Yet, evidence is emerging that Hader himself is part of a vanguard of multi-inning relievers working in the game. Much of the credit for this trend goes to Andrew Miller, who assembled a thrilling set of multi-inning performances during Cleveland’s 2016 march to an American League Championship. But Miller is hardly the face of this high inning relief movement; in fact, when searching for MLB relievers that work at least 1.50 IP/G and work exclusively during relief (Relief IP / Overall IP = 100%), Andrew Miller is nowhere to be found. What is found, however, is that Josh Hader is one of nine long multi-inning relievers working in 2018; for context, the season is hardly a quarter of the way through, and nearly as many long multi-inning relievers are working in 2018 as worked during 2016-2017 (11. See Table One below).

Table One: Long Multi-Inning Relievers, 2013-present (Minimum 1.50 IP / G, 100% Relief IP)

What is striking about this trend is that while the long multi-inning relievers employed in 2013 were mostly quality pitchers judged by Deserved Run Average (DRA), from 2014-2017 the arms were mostly unsavory options, which leads one to wonder whether these relievers were closer to the standard “long mop up option” than 2018 Josh Hader. Now, in 2018, Josh Hader is one of several quality long relievers working.

Table Two: Classic Strike Out Relievers, 1962-1994 (Minimum 75% Relief IP, No IP/G Minimum)

Hader’s absurd strike out performance is also worth noting in terms of redefining this long multi-inning reliever role. Hader’s strike out performance can easily be assessed against classic closers, and while his strike outs are exciting, adjusted for era one can find that there are a classic group of MLB relievers and swingmen who ably exceeded the strike out averages of their respective leagues (Table Two, above). 30 years ago, strike out rates were approximately 35 percent lower than current totals, which means that strike out statistics must be normalized or indexed to the league environment in order to compare performances across eras. Using Baseball Reference League Encyclopedia and Baseball Prospectus historical Individual Pitching Stats by Team, I contextualized strike out performance by indexing a pitcher’s individual strike out percentage (K%) to their league’s percentage. By assessing the “K_Index” alongside innings pitcher per game, one can get closer to normalizing relief performance across time and assessing relief pitching excellence. Thus, although we will see below that Hader’s strike out performance is very good, there is a group of historical arms, especially Rob Dibble, Ron Davis, Bill Caudill, Duane Ward, Lee Smith, and Norm Charlton, who compare quite well to Hader while also working significantly more innings (it will be interesting to see if Hader maintains his early strike out brilliance for a 70-to-90 IP workload).

In terms of assessing workload, the Brewers’ young southpaw has yet to reach the 2.0 inning per game threshold, but there is a “classic bullpen era” (1962-1994) set of pitchers that may serve as an aspirational model for designing Hader’s role moving forward. Table Three (below) lists forgotten relievers that worked from 1962-1994 with at least 2.0 IP per game, sorted by strike out excellence.

Table Three: Classic High Strike Out, High Inning Relievers, 1962-1994 (Minimum 2.0 IP / G, 100% relief IP)

Note that while many of these relievers would not fit “our” current understanding of a closer or high leverage reliever, this group of relievers generally were strike out monsters of their time, compiling relatively high strike out rates during comparably low strike out eras. The DRA follow suit, as 26 of these pitchers posted DRA below 3.50.

Table Four: Modern High Strike Out Relievers, 1995-Present (100% Relief IP)

Assessing “modern” relievers after the beginning of the Wild Card era, it is difficult to find a solid relief role comparison for Hader. Yet, the fun of the southpaw’s strike out performance is that he is an elite pitcher whether one compares his performance with short inning closers or high inning relievers. For example, Table Four (above) demonstrates that Hader’s overall strike out index is better than any modern reliever save for Eric Gagne, and the adjacent presence of Billy Wagner and Aroldis Chapman provide tantalizing southpaw comparisons. Table Four is truly a list of “who’s who” closers over the last 24 seasons, coupled with a few other surprises.

However, part of Hader’s appeal in his current role is that manager Craig Counsell can employ the lefty for six or more outs during a single appearance. This seemingly places Hader in special company within the modern game; after all, only Rafael Soriano, Joba Chamberlain, Francisco Rodriguez, and Troy Percival come close to reaching Hader’s IP / G in Table Four. Thus, it is also worth comparing Hader’s exceptional performance to relievers with similar innings pitched roles. Table Five (below) demonstrates another terrain of the modern game that helps to define Hader’s current value as a reliever.

Table Five: Modern High Innings Workload Relievers Ranked by Strike Out Performance, 1995-Present (Minimum 1.50 IP/G, 100% Relief IP)

Once again, Hader shines: whereas the southpaw demonstrated an extremely high workload among the modern closers in Table Four, in Table Five his strike out rate shines among modern pitchers that worked longer outings. Here, more thrilling left handed comparisons emerge, specifically Norm Charlton and Arthur Rhodes. I also expanded Table Five beyond 30 pitchers to showcase Tyler Glasnow, who is another 2018 high inning reliever posting a very strong strike out rate. While Glasnow’s surface statistics do not appear as great as Hader’s thus far, there are peripheral aspects of the righty’s performance that suggest that he could improve. Together, Hader and Glasnow suggest that there may indeed be a sea change in how managers are viewing relief roles (and, perhaps, how front offices are viewing testy starting pitching prospects with delivery and command concerns). The crucial difference between Glasnow and Hader, of course, is that Hader did not need to fail as a starter prior to moving to the bullpen, and it is worth questioning whether that type of player development decision is crucial to Hader’s success as a reliever thus far.

In 2018, Brewers fans are witnessing an elite bullpen, with Hader undoubtedly serving as the sparkplug and the most exciting graduate out of the farm system. The southpaw served as the sparkplug by covering high leverage situations during closer Corey Knebel’s absence, ostensibly giving Counsell more freedom to be more fluid with bullpen roles after Knebel’s return. Hader is arguably the most exciting graduate out of the farm system not only due to his excellent performance during a playoff run in 2017, but due to his enhancement of that role in 2018. With the caveat that much can change over the course of the season, Hader thus far has rightfully sparked excitement by producing a relief performance that has rarely been seen either from elite closers (in terms of innings workload) or high workload relievers (in terms of strike outs). So where will the “regression” take Hader throughout 2018? Hopefully these tables provide numerous comparisons for the lefty, as well as key role comparisons for how MLB managers can use their arms: there is an entire generation of high workload relievers that are forgotten, falling outside of the praise of the classical closers yet giving hints for how a new generation of arms can be employed. Hader and a group of other 2018 hurlers could serve as the vanguard.

Photo Credit: David Kohl, USA Today Sports Images

References:

Baseball Prospectus. Individual Stats – By Team. CSV retrieved May 20, 2018.

Baseball Reference. League Encyclopedia. CSV retrieved May 20, 2018.