A mechanical flaw may be holding Junior Guerra back this season

Junior Guerra was sensational for the Milwaukee Brewers in 2016. Not only was he one of the top rookie starting pitchers in the National League, but the 2.81 ERA he posted across 20 starts last season placed him among the top first-year arms in franchise history and ranked as one of the top-5 individual performances by a Brewers starter this century.

Unfortunately, Guerra’s meteoric rise from waiver claim to #2016BrewersAce has been matched by a precipitous falloff in production this season. A well-deserved Opening Day start was cut short after 3.0 innings when he tore a calf muscle while running out a bunt attempt and would cause Junior to miss the next 7 weeks of action. He returned to the ball club in late May, but hasn’t looked like nearly the same pitcher that we came to know and love last year.

First and most noticeably, Junior’s velocity is down a great deal from last season. In 2016 his average four-seam fastball was clocked at 94.26 MPH according to Brooks Baseball, topping out as high as 97 MPH. So far this season it’s down to 92.22 MPH and has been trending downward the last few weeks. He’s hit 95 a few times this year according to Brooks, but during his last start he was sitting in the 87-90 MPH range. His other pitches (sinker, slider, splitter) have all experienced similar declines in velocity as well. Perhaps it shouldn’t be altogether surprising that a 32 year old would lose a tick or two off his fastball after throwing the most innings of his career last season, but going from regularly popping the mitt at 95+ to struggling to scrape 90 MPH is most certainly concerning.

A pitcher can generally overcome a loss of velocity if he is able to put the baseball where he wants it, but when Guerra works on the mound this season it seems as though he has little idea where his pitches may end up right now. Even last season his command was fringe-average at times, but this year it’s been downright poor. Guerra’s zone rate of 39.1% represents nearly a 5% drop off from last season and ranks in the bottom-10 among all hurlers who have worked at least 40 innings in 2017. Likewise for his called strike probably of 41.99%, a mark that is about 4% lower than it was in 2016. His first-pitch strike rate is in the bottom-30 of pitchers league wide (min. 40 IP). As a result of being behind in the count so often, Guerra has had to rely more on his diminished fastball and sinker (combined .283 batting average against) at the expense of his still-plus split finger (.160 BAA, 22.6% whiff rate).

The results of these developments have been difficult to watch. True, Guerra was able to grind through several post-DL starts with the help of some good fortune and terrific defense behind him and was carrying a 3.11 ERA as late as June 26th. But his last two starts have been perhaps the two worst outings of his major league career: 4.0 innings, 8 runs, and four homers given up against Cincinnati on June 27th (my oldest daughter’s 4th birthday, no less) followed up by another 4.0 inning stinker on July 2nd against the Marlins with 4 runs allowed. After regression hit all at once in those two appearances, Guerra’s season-long ERA now stands at 4.93 through 45.2 innings pitched. Given his declining strikeout rate (17.3% this season) along with major increases in walk rate (13.5%!!) and home runs allowed (2.36 HR/9!!!), both FIP (7.10) and DRA (8.37) feel that Guerra is extremely fortunate to have produced even his modest 110 ERA-.

Many that have seen these struggles are willing to chalk it up as simple regression. Guerra was a journeyman who spent nearly a decade traveling around the world finding different unaffiliated leagues to pitch in prior to his 2016 breakout, so the easy explanation is that he’s simply reverting to that form. But not only was Guerra terrific last season, he showed the ability to adapt and make adjustments on the fly at the major league level. This is a pitcher who added a new offering to his arsenal - a sinker - in the middle of his rookie year and featured it as a prominent part of his shifting approach to batters in the second half of 2016. Junior has the “stuff” to be a quality major league pitcher when he’s right, and he has shown he has the guile that it takes to keep opposing batters on their heels. That’s what caused me to dig in to Guerra’s struggles a further, and as it turns out, the issue that’s dragging Junior down this season may very well be with his mechanics.

The graph above is an illustration of Guerra’s vertical release point during his major league career. Guerra was highly successful last season throwing from a true three-quarters arm slot, but according to the data from Brooks Baseball his release point on all his pitches is an inch to two inches higher across the board. That may not sound like much conceptually, but here’s what that looks like in real life:

Looking at the two images (both fastballs), there’s a pretty clear difference in the two deliveries. Not only is Guerra’s arm slot much higher in 2017, but he also appears to be driving less with his legs which may be negatively affecting his velocity. Chase Anderson, Jimmy Nelson, and Matt Garza have all found success by lowering their arm slots since Derek Johnson became the pitching coach in Milwaukee, so it seems unlikely Johnson would have taken the opposite approach with his best pitcher from last season. The difference between 2016 and 2017 appears to be a flaw in Guerra’s delivery, and may very well be the root cause for his significant struggles this season.

With this problem identified, there are reasons to be hopeful for Guerra going forward. The team continues to insist that he is fully healthy, and his wife has assured me that Junior feels great physically. He’s actually allowing less hard contact overall this year than he did last season, and his bloated HR/FB ratio of 20% seems likely to come down at some point. Ironing out his mechanical issues may help Guerra recover some of his lost velocity, but even with diminished stuff Junior is still boasting a double-digit swinging strike rate. If he can get his command in order and the walks and WHIP back under control, the ERA should begin to fall back to a more reasonable level.

It’ll be imperative for Junior and ‘DJ’ to work through this issue as the summer goes on. Guerra remains an important piece for the first-place Milwaukee Nine, though the ascendance of both Jimmy Nelson and Chase Anderson (who should return to action in August) means that he doesn’t necessarily need to be the ace that he pitched like last season. But if Junior can recover enough to be at least a steady presence in the middle of the rotation, it may be the difference between Milwaukee being able to stand pat with their starting staff or having to go out and buy an additional arm on the trade market to shore things up for the pennant race.

Junior’s final start before the All-Star break comes tonight against the New York Yankees, so hopefully he can turn in a good outing and build some positive momentum heading into the second half of the season.

Statistics courtesy of Fangraphs and Baseball Prospectus