If you were a young pitcher in 2014, you knew that your arm could dissolve at any moment. That year saw many of the game's up-and-coming hurlers undergo Tommy John surgery, sidelining them for 12 to 18 months and putting their careers in jeopardy. From Ivan Nova and Matt Moore, who received the bad news in April; to Jose Fernandez, who went under the knife in May; to Tyler Skaggs, who had the procedure done in August — it amounted to an epidemic.
Among all of those big names, Patrick Corbin may have gotten lost. He beat them to the punch, as his Tommy John surgery occurred in March; upon returning, he's excelled despite little fanfare. Whereas men like Moore and Nova have struggled to regain their form, Corbin has adopted a whole new recipe — and found new levels of success with it.
That isn't to say Corbin did poorly pre-injury. As a rookie in 2012, he pitched his way to a 111 ERA- and 95 xFIP- over 107.0 innings. Those marks improved to 88 and 92, respectively, in his sophomore 2013 campaign. Striking out 20.1 percent of batters while walking 6.0 percent in that span, he prevented them from putting the ball in play and from reaching base. When they did make contact, it stayed on the ground 46.3 percent of the time, a clip that helped him avoid homers in hitter-friendly Chase Field. All in all, it made for a perfectly solid pitcher.
Come 2015, the batted-ball distribution hadn't shifted: Corbin accumulated 46.9 percent grounders in his 85.0 frames this year. In terms of strikeouts and walks, though, he took things to the next level. 21.9 percent of the men who faced Corbin in 2015 went down on strikes, while just 4.8 percent earned a free pass. That combination netted him an ERA- of 88 to go along with an xFIP- of 84, the latter of which was far lower than his 2012-13 figures — and good enough for 27th in the majors among pitchers with 80 innings. Pitching to the level of Matt Harvey and Carlos Martinez, Corbin has become a star.
These changes happened in two key areas. Baseball-Reference's data show that Corbin bettered his strike rate slightly, which went from 65.8 to 66.6 percent, and his swinging-strike rate, which went from 10.8 to 11.9 percent. More strikes meant he'd issue fewer bases on balls, while more whiffs (and more strikes as a whole*) meant that he'd rack up the punchouts.
*Mike Podhorzer has connected strike rate to strikeout rate.
On a pitch level, Corbin altered several things. Before his injury, he used a sinker as his bread-and-butter pitch, mixing in some four-seam fastballs as well. 2015 saw him reverse that trend:
Suddenly, the four-seamer became Corbin's primary offering, while the sinker fell to number 2.
The sinker doesn't fool hitters very frequently, with a lifetime whiff rate of 5.4 percent, so it didn't make much of a difference there. On the flipside, the four-seamer has given opponents fits, especially recently:
The four-seamer's swinging-strike rate peaked at 7.9 percent in 2015, which had a lot to do with Corbin's strikeout surge. A spike in its overall strike rate, from 62.4 to 66.8 percent, also helped with the drop in walks.
Oddly enough, however, Corbin didn't place the four-seamer that differently this year — it still traveled primarily to the middle left of the plate, as it did before. The change came from its partner in crime, the sinker, which moved downward significantly:
The plate-scraping sinkers contrasted to a much greater extent with the four-seamers, which left hitters guessing. Low pitches obviously don't miss many bats, and Corbin's sinker followed that rule — its whiff rate dipped to 4.8 percent in 2015. With those extra swings-and-misses on the four-seamer, though, he didn't need anything more from the sinker.
Of course, 7.9 percent whiffs won't allow a pitcher to fan many people. Corbin's biggest swinging-strike pitch has always been his slider, which owns a career rate of 26.0 percent in that regard. In 2015, Corbin wisely decided to deploy that a good deal more:
Like the four-seam fastball, the slider also went for strikes more often in 2015 (68.5 percent of the time) than it did in the preceding seasons (64.9 percent). This, along with those whiffs, made it the deadliest pitch in Corbin's arsenal.
Corbin's slider presents an intriguing case. In 2015, 87 starting pitchers threw at least 200 such pitches; out of them, Corbin ranked:
- 70th in velocity (81.9 MPH);
- 86th in horizontal movement (0.3 inches);
- 70th in vertical movement (-0.4 inches); and
- Sixth in whiff rate (24.0 percent).
One of these, quite clearly, is not like the others. Corbin somehow received spectacular output from subpar stuff — but how?
Like the four-seamer, Corbin's slider derived its superiority from its relative location. He's always thrown it to the same place:
This diverged notably from his four-seam fastball, which went higher, and his sinker, which tailed to the right. Together with its vastly distinct movement, this pattern didn't give hitters a chance.
The slider itself didn't change at all in 2015. It still dominates in the same manner it did before, when then-Diamondback Miguel Montero described its ability thusly:
"He's able to get it in and get it out. They start looking for a fastball in or a fastball away, and then there comes a slider with the same arm speed. It's hard to lay off that good of a slider."
That contrast simply occurred more often this year, and the results proved that it was worth it. Benefiting from a clean bill of health, the four-seam/slider version of Corbin took the league by storm.
Tommy John surgery doesn't kill careers like it once did. Fernandez certainly didn't miss a beat when he hopped off the DL (although he may have created some other problems). For Corbin, no known off-field issues exist, and the on-field production can't get much better. The Diamondbacks don't have very many capable major-league pitchers, but in Corbin they seem to have found themselves a budding ace.
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