Justin Wilson has had a polarizing season for the Tigers out of the bullpen. While many advanced metrics will show that he has been a borderline elite reliever — he has a 2.79 FIP, a 2.66 xFIP, and has been worth 1.2 fWAR — his 4.37 ERA will state otherwise. On any given night, Wilson could look flat-out dominant, overpowering both lefties and righties with his fastball/cutter combination.
However, he has also had his fair share of meltdowns. His back-to-back implosions in Seattle two weeks ago set the tone for two infuriating, and possibly season-changing losses. After that series, the Tigers released information stating that Wilson had been dealing with a sore elbow, which is the second documented time this season he has been shelved for it.
On August 15, Wilson received a cortisone injection in his left elbow. Prior to receiving the injection, he had pitched three straight atrocious outings, allowing six earned runs and two home runs in only 2 2⁄3 innings. Since he returned from his week-long rest, he has looked dominant again, striking out five batters in 3 2⁄3 innings.
Wilson has thrown a total of 58 pitches since returning from elbow soreness. Of those 58 pitches, none have been breaking balls. Initially, I thought that he wasn’t throwing them because he doesn’t want to re-aggravate his elbow for a third time this season. However, when you look at his PitchFX data over the last three years, he has never thrown his breaking balls more than seven percent of the time. It’s still possible that he scrapped them because they make his elbow sore, but not having them in his arsenal really doesn’t change who he is as a pitcher.
Wilson’s four-seam fastball, a pitch that averages over 95 miles per hour from the left side, has been his bread and butter since coming to the big leagues. Partner that with a wicked cutter that sits around 90 mph and a hard sinker, and you have a threesome that most lefthanders would pay to get involved in. While a five mph difference between pitches isn’t enough to throw off the hitter, the difference in the movement between the four-seam, cutter, and sinker allows him to dominate without changing speeds.
One possible explanation to Wilson’s struggles could lie in the movement of his cutter. While the small difference in velocity from his four-seam is nice, its movement is what generates off-balance swings. Vertically, the movement has been constant this season, but it isn’t moving as much horizontally. When Wilson’s cutter isn’t tailing in on right handed hitters, or tailing away from left handed hitters, it simply stays in the middle of the plate practically begging to be hit.
As you can see, he has lost some of the tail on his cutter over the last two months. While it’s starting to get back to where it needs to be, some damage has been done against it. The highest ISO he had allowed against his cutter in any month was previously .091 in May. In August, the ISO against is currently .291. “But wait, his cutter had significantly less tail in July than it does in August?” is a question you might be asking yourself. Great question! His ISO against his cutter in July? Zero, the same as the number of breaking balls he has thrown since his cortisone shot.
It’s still possible that Wilson’s cutter movement has had something to do with his weird stretch, but the statistical evidence doesn’t do a whole lot to back it up. Maybe it’s his four-seam fastball that’s causing his problems? Judging by the chart, his four-seam fastball movement has also subtly declined, and opponents have a blistering .750 ISO against it in August. That can’t all be because of a subtle difference in movement, right? Right.
Since Wilson was shelved in mid-June with his first reported case of elbow soreness, his four-seam fastball velocity is down nearly one mile-per-hour. His cutter velocity is also steadily declining, though. These are both subtle differences, but they’re still notable.
Looking at both the movement chart and the velocity chart, it’s easy to see the declines in both for his four-seam and his cutter. It doesn’t look like a lot on the surface, but I might have an educated guess as to why he’s being hit around lately, and why his peripheral statistics differ from the numbers on the surface. Being a pitcher who exclusively uses fastballs, Wilson needs to be able to throw them with consistent velocity, command them, and generate lots movement. If any one of those are off on any given night, he doesn’t have a breaking ball to fall back on and get him out of trouble.
When his fastballs are on, Wilson is untouchable regardless of opponent. However, you can say that about most of the elite relievers in baseball. Craig Kimbrel? Yep. Dellin Betances? Oh yes. Andrew Miller? You betcha. Aroldis Chapman? Hell yes. But what separates those four is the fact they all have a devastating off-speed secondary pitch. Wilson’s secondary pitch is another variation of the fastball. I’m well aware that Mariano Rivera turned himself into the best closer in baseball history using a simple cutter/sinker combo, but he is the outlier of all outliers, not the norm. For Wilson to have consistent success, it would seem wise to develop his slider or curveball to the point of being able to use it to, at the very least, change speeds on a hitter.