Sonny Gray Has Mastered the Kitchen Sink Approach to Pitching

After trading for Sonny Gray on November 25, the Boston Red Sox believed they had acquired the No. 2 starter in their rotation. Through his first five starts, however, it appeared that age may have finally caught up to Gray. He posted a 5.09 K/9 and surpassed four strikeouts only once, in his season debut, giving him the fourth-lowest strikeout rate among qualified starters during that span. Then, Gray tweaked his right hamstring, and it seemed his season might go from bad to worse.

That has not been the case.

Since returning on May 6, Gray has pitched at least five innings in all three of his starts while allowing just two runs across 17 innings. Most importantly, he has set season highs in strikeouts in consecutive outings, recording six against the Phillies before striking out nine Royals on Monday.

After opening the year with five straight starts of three strikeouts or fewer, Gray doubled his season strikeout total in just two outings, increasing it from 15 to 30.

Following Monday's start, Alex Speier of the Boston Globe asked Gray what had changed to produce the swing-and-miss results he had been seeking:

"Anything you're seeing in terms of those strikeouts?" he asked, "Obviously a bunch of swing and misses tonight were on the sweeper, a couple on the curveball. Is it just executing spin better, or is it how you're tunneling?"

Gray's response consisted largely of noncommittal answers, seemingly intent on keeping the details of his success close to the vest. Fortunately, the wealth of publicly available data gives us an opportunity to investigate what may be different.

Pitch usage provides an obvious starting point. When comparing Gray's pitch mix before and after his return from the injured list on May 6, several notable changes emerge.

The char above compares his pitch usage from March 28 through May 5 (top) with his usage from May 6 through May 18 (bottom).

We can see that Gray's sweeper and four-seam fastball essentially traded places in usage. His sweeper usage increased from 15.9 percent to 18.9 percent, while his four-seam usage dropped from 18.2 percent to 15.8 percent. The adjustment makes sense. Throughout his career, Gray has relied heavily on breaking pitches to generate outs, and last season his breaking balls produced a 97th-percentile run value while the rest of his arsenal graded out below average.

If Gray's goal was to generate more strikeouts, leaning on the sweeper was a logical move. Before the injury, it generated the highest swinging-strike rate among any pitch he threw more than 10 percent of the time. Since returning, it has remained his best bat-missing offering, producing a 20.9 percent swinging-strike rate. He's also simply thrown more strikes overall, which naturally creates more opportunities to finish hitters with strikeouts.

One area worth monitoring is how these changes affect his batted-ball profile. His ground-ball rate has declined significantly, while his line-drive rate has climbed. That shift could lead to more hits falling in, but it may also be the trade-off required to maintain the elevated strikeout numbers we've seen since his return.

It's difficult to draw firm conclusions from only three starts. Still, for a pitcher whose success has long been built on a kitchen-sink approach, throwing more pitches with movement is likely to produce better results. At this stage of his career, increased fastball velocity is unlikely to be part of the equation. If Gray is going to continue missing bats, it will be because he leans on his elite breaking stuff. The early returns have been encouraging. Now, we'll see whether he can sustain them and continue serving as a stabilizing force in the Red Sox rotation.