One of the most important things on contending teams isn’t just the superstars, it’s the role players that break out of their mold and excel. That’s really what can carry a team to a division title and into a deep postseason run. For example, there was Charlie Morton on the Astros in 2017 and Edinson Vólquez on the Royals in 2015. These guy broke out when their team needed it the most. Arizona Diamondbacks starter Patrick Corbin is on a similar path. He’s considered a journeyman, but I think that is about to change. Corbin, who hasn’t really been known for strikeouts, is currently fifth in the majors in strikeout rate.
Tommy John put him on the shelf for the 2014 season, but he has rebounded and in a big way. Last year, he posted solid numbers with an ERA of 4 and a FIP that matched, and his strikeout rate came up and his walk rate went down. He stranded more runners on base and took his home run rate down a tick. All in all, he took a well-portioned step in 2017 to becoming even more successful than he already was.
Those type of numbers almost look laughable to what he’s doing this year; everything has improved even more than between 2016 and 2017. The two numbers that really caught my eye were strikeouts and batting average. His batting average against went from .273 last year to .186 so far this year. That’s incredible, and speaking of incredible is his strikeout rate of 33 percent.
When I first looked at his numbers, especially that 33 percent strikeout rate, my initial thought was: this isn’t sustainable. However, once I dove in deeper I saw something that completely changed my mind. He’s added a curveball this year, and not just any curveball either, a pretty good one at that. He’s throwing it 13 percent of the time and getting a swing rate over 30 percent. Plus, his whiff per swing rate is almost 35 percent. It’s incredible for someone who just debuted the pitch at the start of the season.
Although before researching, it seemed like he had this in his back pocket and just lacked the confidence to throw it in games, which is likely the case given it’s success and the fact that back in 2013 he threw two of them. Neither Statcast nor BrooksBaseball has him throwing any other curveballs during major league appearances. However I did find something interesting. Back in 2011 he went on a scoreless streak that reached over 19 innings in High-A. He chalked the streak up to his developing knuckle-curve, so it’s obvious he used it in the minors, he had just yet to flash it at hitters in the majors.
One number that really assists with making my judgement on pitchers is SIERA, although one metric cannot tell you everything about a pitcher; if your SIERA is low, below 3, you’re not just doing one or two things well, you’re doing basically everything well, which is really what has sold me on this not just being a hot streak but rather a transformation into a more reliable and dominant starter. Another huge factor from what I’m seeing is he’s all but abandoned his changeup, which he used close to ten percent of the time last season. We’ve seen guys like Justin Verlander do that as well, which seems to aided in their success. This allows them to work on it in side-bullpens and spring training until they get a better feel for the pitch.
There are a couple of things that strike me as unsustainable, however. First is he’s actually getting less soft contact and more hard contact this year. His hard contact rate has jumped almost ten percent since last year. This means once luck or chance shift, those hard contact will turn from deep flyouts and hard groundouts into extra base hits and home runs. Secondly, his BABIP of .249 is helping the huge drop in batting average against. So those numbers will likely change but I don’t see huge changes in them on the horizon, rather slight shifts back to the norm. Ironically his xFIP is lower than his ERA so there could be some decently good numbers like his home run per fly ball rate, that shift back to his favor to balance out any changes in other numbers.
His out of zone swing numbers are the same as they were the past few seasons, so either he’s not throwing his breaking stuff out of the zone enough or batters just aren’t swinging at it. The good thing is he has dropped his out of zone contact rate by 12 percent which lends credence to the fact that curveball is aiding his swing and miss stuff.
However, the heat map is showing that he’s throwing a good percentage of the pitch inside of the zone and his wOBA is .372 which doesn’t spell well for a season of success. It could be a Cain & Abel type of thing where it’s either swing and miss or barreled up, but you’re basically playing Russian Roulette at that point given the uncontrollable factors of baseball. Additionally his slider is also being thrown in the strike zone often as the heat map below shows.
Luckily for him, the slider only has a .207 wOBA and is getting a whiff rate of almost 30 percent. Despite some warning signs, I believe the success for Patrick Corbin is absolutely sustainable. The biggest factor for him is to get that curveball out of the zone, or at least throw it so that hitters aren’t making as good of contact as they currently are. If he can put the curveball in better locations and also keep the average against the slider down as he currently is, look for him to continue this success throughout the season and even repeat it next year. This gives the Diamondbacks a prime opportunity to take the division and make a deep postseason run in the fall.