A suggestion to fix Sonny Gray

Sonny Gray is one of baseball’s biggest enigmas.

In 2015, Gray was a 25-year-old American League All-Star, leading the Athletics with a 2.73 ERA across 208 innings pitched. He finished third in the Cy Young award voting, and had seemingly cemented his place among the best young pitchers in Major League Baseball. With a bright future ahead, many were excited to see Gray improve across the course of what looked to be shaping up as a brilliant career.

Sure, perhaps I am overstating Gray’s performance just a tiny bit. From 2014 to 2015, he did only rank 26th out of 84 pitchers in fWAR, though he was 10th in the majors in RA9-WAR during that stretch. Nonetheless, it was still exciting to see a mid-20s pitcher putting up dominant numbers in the American League.

Gray has fallen far from grace in the years since. His strikeout-to-walk numbers have remained relatively constant, but he has allowed a much higher hard-hit rate. With that, he’s struggled to keep the ball in the ballpark, allowing at least one home run per nine innings in each of the last three years. His BABIP allowed, too, has gone up.

The Athletics traded Gray to the Yankees in 2017. They hoped that they could recover some of the magic. It hasn’t worked.

In 2018, Gray was so bad during his first 21 starts (5.56 ERA, .788 OPS allowed) that the Yankees demoted him to the bullpen for the remainder of the season (though he did make two spot-starts). While solid down the stretch, Gray still put up a 4.90 ERA and a 4.17 FIP in 130 ¹⁄₃ innings overall, a far cry from the pitcher who once had an ERA 2.17 points lower and a FIP 0.72 points lower.

Yankees GM Brian Cashman has made it clear that he would like to trade Gray, reiterating to Bryan Hoch of MLB.com again on Friday that the team’s “intention is to move Sonny Gray and relocate him.” However, it is still a possibility that Gray remains with the Yankees into the beginning of the season.

No matter which team Gray begins (or ends) next season with, I have one suggestion that could significantly improve his results.

Gray needs to take the Patrick Corbin approach to pitching.

What does that entail, exactly?

It’s pretty simple, though certainly much easier said than done: Gray needs to completely overhaul his pitch frequency.

Since 2015, Gray’s slider has a .194 xwOBA allowed. That ranks 17th out of 195 pitchers who have faced at least 200 batters with it. It’s been as good as Max Scherzer’s slider in that stretch. Scherzer, mind you, has posted strikeout rates of 36, 43, 50 and 38 percent using the pitch in the past four years. Gray’s slider, to say the least, is elite.

I present this hypothesis: if Gray turns his slider — his best pitch by far — from a weapon into his most frequent offering, then we could see his performance take off.

This theory was tested best by Patrick Corbin, whose .201 xwOBA against his slider since 2015 is actually worse than Gray’s. Still, Corbin’s best pitch has always been his slider, and in 2018, he decided to throw it more. A lot more:

Corbin threw his slider nearly 41 percent of the time in 2018; FanGraphs reports that he ranked second among qualified starting pitchers in slider usage.

The results spoke for themselves. Corbin’s slider remained outstanding, generating a .145 batting average against and 195 strikeouts. He only walked 4.2 percent of batters with the pitch. This resulted in a career-high 30.8 percent strikeout rate for Corbin, a career-low 6.0 percent walk rate and a 2.47 FIP (60 FIP-). In one year, Corbin took himself from a solid mid-rotation starter to an ace that the Nationals were willing to pay $140 million to.

I (unfortunately) cannot guarantee that Gray would benefit from similar results. Here is how his pitch frequencies have looked over the past six years:

A stark difference between Corbin and Gray is that even when Corbin wasn’t throwing his slider as his most frequent pitch, it still ranked second or third. The slider was Gray’s fourth-most common pitch last season, demonstrating that it would need a serious ramp up in order to move into the top spot.

But, during the two seasons in which Gray threw the most sliders — 2015 and 2017 — his results were generally solid. The former was the best year of his career, while the latter was a rebound year after a terrible 2016. However, I’m not sure that this is necessarily good evidence that Gray’s slider is the reason for these solid performances, especially considering his slider pitch rate hasn’t really been significantly lower in the down years.

Still, though, Corbin threw more sliders in 2018 (1,285 sliders) than Gray has thrown in the past three years combined (1,025).

How much could a change like this impact Gray’s performance?

I’d say pretty significantly. If we play with the numbers for a minute and invent a hypothetical in which Gray’s sinker (his most frequent pitch in 2018) and slider were switched in terms of frequency, but with the same results, Gray would have allowed eight fewer hits (taking his BAA from .267 to .251), would have struck out 31 more batters (taking his strikeout rate from 21.1 percent to 26.5 percent) and would have walked just one more.

While these numbers were obviously hypothetical, there is a nonzero chance in which Gray becomes significantly more effective with a change to his repertoire. Of course, it would require a lot of work, a lot of trial-and-error and a lot of unknown to see if a “Patrick Corbin approach” could work for Sonny Gray, but considering how he has pitched in the past couple of seasons, it’s still an option that’s worth trying in an attempt to return him to stardom.

Devan Fink is a Featured Writer for Beyond The Box Score. You can follow him on Twitter @DevanFink.