Patrick Corbin was named the National League Player of the Week this week and it is an award well deserved. Corbin has been fantastic so far for the Diamondbacks. He was a surprise opening day starter for the Diamondbacks but he has thrived in the spotlight. In 2018, Corbin has four wins in five starts striking out 48 in 33 1/3 innings with 1.89 ERA. The impressive thing about what Corbin is doing is that his FIP and xFIP are just 1.99 and 1.69, respectively. Those numbers demonstrate that Corbin’s strong start is all about him and not about great defense rescuing him. He has never struck out more than a batter an innings in a full season in his major league career. The two questions are; what is Corbin doing that has suddenly made him unhittable? And can he sustain this success over the course of a full season?
Some quick observations: Corbin’s control is currently close to matching his best ever in his career. In 2015, his walk rate was 4.8 percent and this season it is 4.9 percent. Comparing that to his career rate of 6.9 percent, it calculates as one less batter walked per nine innings. It is nothing major but it certainly doesn’t hurt. In terms of his batted ball profile there is little difference in line drive, ground ball and fly ball rate from last season. In addition, his home run to fly ball rate is virtually identical to last season.
Pitch usage data is from Fangraphs with pitching outcomes from Brooks Baseball.
The humidor
It may be early in the season but the humidor certainly does seem to be having an effect. AZ Snake Pit looked at the numbers as of Friday the 21st of April, which is 10 starts with the humidor. Obviously, it is a small sample size but here is a summary of the results. Across 765 plate appearances, there has been a 39.5 percent drop in runs. Chase Field now has the second-lowest OPS in the NL (.643), having been third highest in 2017 (.773). There has also been a drop in home runs from one ever 28.5 PAs to one every 38.2. Interestingly, BABIP has also reduced from .306 to .262. It might just be too early to draw any conclusions especially given that hitting usually increase as the temperature ramps up. However, the humidor does seem to be having an effect.
Corbin has always been a better pitcher in Arizona than on the road but that is even more apparent now. He currently has a .376 OPS against and a 1.19 ERA at home compared to .554 and 5.06 on the road. Again he has only made four home starts and one road start so it is a small sample size. However, the splits will definitely be something to watch with Corbin, especially for fantasy owners and DFS players.
His pitch mix
Last week, I broke down Gerrit Cole’s pitch mix this season compared to last and there were some significant differences. Well, for Corbin, the change is perhaps even more apparent. Not only has he completely changed his usage of three pitches from last season but he has also added a completely new pitch.
His four-seam fastball usage is down nearly 14 percent on his career numbers, 16.7 vs. 30.4 percent. His sinker is now his main pitch which averages over 90 mph and is thrown 31.3 percent of the time. That is an eight percent increase on 2017 but matches his career numbers. His slider remains his most used pitch at 40.8 percent. That is a just 2.8 percent increase on 2017 but a whopping 12.8 percent on his career average. The pitch he has all but abandoned is his changeup which he has thrown just twice in 33 1/3 innings. He has replaced his changeup with his new curveball, which he is throwing on 10.4 percent of his pitches.
So can you guess which of his pitches gave up the most home runs last year? Yes, it was the changeup which was hit for a home run 1.93 percent of the time. That is nearly double the next highest, his four-seamer, at 1.05 percent.
His new curveball has been dominant so far, with just one ball in play in the 50 he has thrown. In contrast, he has had a 46 percent strike rate and an 18 percent whiff rate with that pitch. However, the slider remains his most effective pitch with a whopping 33.16 percent whiff rate. As long as we keep seeing numbers like those expect Corbin to keep throwing it 40 percent of the time going forward.
Conclusion
With any pitcher who improves drastically from one season to the next, there is often not just one element. For Cole, it was his pitch mix and a move to a new league. For Corbin, it is likely that this start is a combination of a radically different pitching strategy and the humidor. It will be interesting to see how he fares over his next few road starts. If he struggles away from home then we can likely say the humidor is the key factor. However, if he has some good road starts then the major contributor is probably the new look pitching arsenal.
