Grading Future Guerra: Strike Zone

Yesterday, Brewers rookie Junior Guerra had a rough outing at PetCo Park. Few will remember his nondescript four run, four inning outing for its performance, but the righty’s start was significant for another reason: Guerra has now started the most games of any age-31 debut starting pitcher in the MLB divisional era (1969-present). Guerra’s season has been “one of a kind” from the get go, and now it’s quite historical.

Related Coverage:
The Call-Up
The Splitter
Guerra Might Be For Real
Guerra Is Clutch

Of course, what makes Guerra’s historical season so much more interesting is that the righty has served as the best starter in Milwaukee’s rotation. In fact, Guerra’s runs prevention performance is one of the factors spurring an above average staff from May onward. Weighted against Miller Park and the 2016 National League, Brewers hurlers have been approximately 16 runs better than average since their dreadful April performance. Entering San Diego, Guerra’s 3.75 DRA was nine runs better than his league and park, spurring a significantly above average campaign.

Brewers fans clamored for Guerra to be traded at the deadline, rather than have the Milwaukee Nine hang on to their history-making ace. The argument about Guerra’s trade value typically takes three stages or formats: (1) At age 31, Guerra’s future performance cannot be reasonably projected because he is already “old;” (2) Guerra has never produced at this level prior to 2016, and therefore it is unsustainable; and (3) the Brewers are not going to be a competitive team, so Guerra’s value is “wasted” (or, more useful elsewhere in return for future value prospects).

There are several problems with these arguments, not the least of which is vulgar age determinism, but the issue of grading Guerra’s future value is legitimate. First, if the Brewers believe that the righty has a specific outlook, keeping Guerra in the rotation could help hasten the rebuild. Fans seem to hate this argument, but it’s true: once the Brewers begin finding good players and keeping them, they shorten the rebuild. Jonathan Villar shortens the rebuild; Zach Davies shortens the rebuild; Tyler Thornburg shortens the rebuild; and, of course, Guerra shortens the rebuild. Furthermore, the Brewers simply do not need to grade Guerra as a starting pitcher. If his profile fails to project well in that role, the Brewers could move the righty to a relief role, where his splitter could thrive as he heads deep into his 30s.

To counteract arguments in favor of shedding Guerra, there are several aspects of Guerra’s performance that one can analyze. This particular discussion will focus on Guerra’s strike out and K / BB profile. A second feature will encounter the aging development of other extreme splitter pitchers, and Guerra’s own personal development. Together, these counterarguments will establish a future grade for Guerra.


Age 31 Strike Zone Performance

Since the turn of the century, 101 qualified pitchers have worked in the MLB during their age-31 season. Not surprisingly, among these pitchers, Guerra is posting quite a noteworthy season: the righty is a member of a select group of qualified pitchers that have reached 7.4+ K/9 and 2.5 K/BB during their age-31 campaign (stats compiled prior to San Diego start). From 2000 through 2015, only 30 pitchers reached this strike out and walk level during their age-31 campaign.

Reaching 7.4 K/9 or 2.5 K/BB by itself is not necessarily that exciting, as either mark is basically around or slightly below average in the contemporary MLB. Yet, in terms of age-31 pitchers, less than a third of the qualified pitchers from 2000-2016 have reached that level of combined strike zone control at that age. By age-31, a pitcher may be sticking around in the MLB on guile or a refined approach that does not necessarily need high strike out or strong K / BB rates (or, of course, at that age even a qualified starter might perform according to a low rotation or replacement profile).

How do these pitchers age? This question is crucial to grading Guerra’s future role, for if the righty can follow specific strike out and walk trends, that arguably suggests that Guerra has mitigated command issues or continued to attack batters in a way that makes his command less problematic. The assumption here is that if a pitcher has a certain type of stuff, and a certain type of strike zone profile, his aging will be defined by the development of that strike zone profile.

I focused on 29 of those age-31 K/BB pitchers (excluding 2000 Darryl Kile) in order to judge their strike zone performance through age-31, and after age-31 seasons. These 29 pitchers produced 280 seasons through age-31, and 116 seasons (thus far) from age 32 onward (several pitchers, including Cole Hamels, Zack Greinke, CC Sabathia, and James Shields, are still in the midst of their careers, which accounts for some of the post-31 drop off).

29 K/BB and K/9 Comps Seasons G / Season IP / Season K / BB K % / BB %
Through 31 280 27.9 168.7 2.88 20.5 / 7.1
Age 32 and After 142 20.0 119.7 2.95 19.8 / 6.7

Through their age-31 seasons, these pitchers compiled 142 seasons of 7.4 K/9 and 2.5 K/BB baseball (51%); from age-32 and onward, they compiled 79 seasons with that strike zone profile (41%).

Notably, even including injury-shortened or interrupted mid-to-late 30s performances, or role changes in some cases, this group of strike zone control pitchers maintained their strike out and walk performances as they aged. What surprised me was that these pitchers often found ways to lower their walk rates as their strike outs faded.

Of course, in one sense these numbers are dominated by elite starting pitchers that do not provide any useful comparison for Guerra. For example, Cole Hamels has surpassed the 7.4 K/9 and 2.5 K/BB mark in each year of his career; he is the only pitcher in this group that has accomplished that feat. Along with Hamels, Pedro Martinez, Greinke, Josh Beckett, Jake Peavy, Javier Vazquez, Sabathia, Shields, Adam Wainwright, and Wandy Rodriguez dominate the 7.4 K/9 and 2.5 K/BB seasons through age-31. These pitchers are different from Guerra in many different ways; they have often been touted prospects, starting pitchers from their early 20s onward, and have therefore landed several of the largest pitching contracts in MLB history.

Excluding this group of players leaves 18 pitchers worth comparing with Guerra (I excluded Dan Haren, who snuck into my study as a 7.2+ K/9 and 2.5+ K/BB pitcher at age-31. WHOOPS!). Among this group of pitchers, 11 have completed their careers, posting an average WARP of 18.0 from age-32 and beyond.

Strike Zone Comparison Total 7.4 K/9 2.5 K/BB Seasons Thru 31 After 31 WARP (Before / After 31)
Pedro Astacio 4 28 / 30 / 31 32 34.0 / 9.9
Mike Mussina 9 27-31 32 / 33 / 34 / 37 58.0 / 46.3
Esteban Loaiza 1 Age 31 n/a 19.6 / 7.5
Andy Pettitte 5 30-31 32 / 34 / 40 32.1 / 31.2
Jason Schmidt 3 29-31 n/a 29.7 / 5.8
Chris Carpenter 3 29-31 n/a 31.7 / 13.4
Ted Lilly 7 23 / 27 / 31 32-35 20.9 / 16.2
A.J. Burnett 8 27-31 35-36 / 38 30.2 / 20.4
Roy Halladay 7 21 / 24 / 31 32-35 44.9 / 23.5
Aaron Harang 4 28-31 n/a 21 / 0.8
Cliff Lee 5 31 32-35 31 / 23
Colby Lewis 3 30-31 32 Incomplete
Joe Blanton 5 28 / 30-31 34-35 Incomplete
Ervin Santana 2 25 / 31 n/a Incomplete
Jason Hammel 4 29 / 31 32-33 Incomplete
Scott Kazmir 6 22-23 / 29-31 32 Incomplete
Francisco Liriano 5 21-22 / 26 / 29 / 31 n/a Incomplete
Jon Lester 6 25-26 / 29-31 32 Incomplete

It is worth noting several qualities among these pitchers.

  • Some pitchers bloom late, even when they are in the MLB during their 20s. In terms of strike zone control, this is arguably true of Cliff Lee, Ted Lilly, and Roy Halladay. Note that each of these pitchers relied on moving pitches and “guile,” rather than pure stuff.
  • Other pitchers maintain their value quite well into their 30s, even as their stuff changes. Mike Mussina is a perfect example of this, as the righty found ways to stay in the MLB even as his sinker velocity descended closer to 80.0 MPH than 90.0 MPH.
  • Injuries can be an issue, but they are not always a “kiss of death” for a pitcher’s career. Joe Blanton and Colby Lewis are instructive examples here.

The Systems Pitcher

Most notably, in the “Age of Analytics,” one ought to consider the impact of a “Systems Pitcher” in the MLB. Jason Hammel and A.J. Burnett are arguably the best examples of this trait of pitcher on this list. Burnett was weathering some tough seasons in the Bronx prior to heading to the Pirates, who helped realign Burnett’s pitching strategy (see Travis Sawchik, Big Data Baseball). Incidentally, his solid K/9 and K/BB seasons at age-35, 36, and 38 each occurred with the Pirates. Similarly, Jason Hammel has also served as a particularly useful pitcher for the Cubs, even heading into his 30s. The Cubs liked Hammel so much for their system that they re-signed him prior to 2015, after using him as a trading asset at the 2014 deadline.

Even slapping the 18.0 post-31 WARP price on Guerra provides a crude but useful mechanism for the Brewers. Should Guerra come anywhere near this number, be it as a reliever or as a starter, he will provide tremendous value for Milwaukee, particularly considering the fact that he can be renewed at $1.1 million between 2017-2018, and then face salary arbitration some time thereafter. Acquiring such a pitcher would cost anywhere from an extremely conservative estimate of $32 million, to much more expensive or even absurd-sounding estimates (the most expensive estimate tops out well into the nine figures, which I am embarrassed to even publish. This is video game stuff).

Moreover, if one believes in the power of a “Systems Pitcher,” one has to trust the Brewers’ vast system of biomechanical research and their biomechanical database, alongside their approach with the righty’s pitching strategy. The White Sox organization deserves credit for bringing Guerra back into the fold of affiliated baseball, but perhaps the Brewers have found the elixir for success for the uncanny rookie. Guerra has already learned a sinker to adjust his approach with the Brewers during 2016, which shows a concrete ability to fit the needs of a system (yield groundballs for heavily shifted infields) and to improve a problem at the MLB level (shift from a flyball pitcher to a groundball pitcher). Given that it is not terribly rare for some pitchers that rely on movement and strike zone control to emerge into their prime during their 30s, hanging an exceptionally steep price on Guerra is the correct choice for Milwaukee.

Related Articles

2 comments on “Grading Future Guerra: Strike Zone”


Thanks for the sanity. There are also some factors that are difficult to measure that don’t have a place in this analysis, but I’ll throw them out for comment. The light career IP totals. If teams voice concern over young Ps season inning limits, or SPs with accumulating 200 IP season, or RPs with 60 GP for 4-5 years, the reverse concept must also apply- Guerra has a lot of innings left.
Then there’s the advantage of being a former C. In his vast experience around the world he’s seen and discussed all the pitches, from all angles. Mentally, he knows how to pitch, a trait that ages well. If he wants to rest his arm from the strain of a splitter after a couple months he just replaces it with a 2-seam sinker. He probably throws a mean cutter as well.
As a C and hitter he knows what it means to make adjustments, and tweak new pitches. Like a pitching coach, he has discussed the mechanics of all aspects of pitching for years and can self-correct and re-invent himself. And now for the next Juni article [to read]

Leave a comment