Back in April, after an ugly start to his season, I wrote that in order to return to form, Kevin Gausman might need to make an adjustment. Early on, his fastball velocity was inconsistent, jumping from 96 mph to 89 mph within the same start. Because he relies almost exclusively on just two pitches, I figured if the fastball faltered even a bit, it might lead to trouble.
To this point, these concerns have been justified. As June came to a close, the fastball velocity was down about a tick; after allowing seven runs against the Yankees, his ERA sat at 4.75. To save his season, he needed to figure something out. And in his latest start, he might have done just that.
To be fair, it was against the Mariners, so perhaps the 17 whiffs and 11 called strikes on the four-seam fastball should be taken with a grain of salt. But those results can’t be fully attributed to the Mariners’ demoralizing offense. There was something else going on. Gausman succeeded because he made an adjustment — but not the kind of adjustment I’ve come to expect pitchers to make.
In a great story for MLB.com, Blue Jays beat writer Keegan Matheson noted that between his June 30 start against the Yankees and his July 5 start in Seattle, Gausman made a rare midseason mechanical tweak. From Matheson:
The simple version is that this starts with Gausman’s setup. Gausman tried to be more “hunched over” on the mound, he said, and by hunching his back and dropping his posture a bit, this allowed him to lower his arm angle.
The change to the starting posture is clear. Here’s Gausman on June 30, standing straight up with a firm posture prior to delivering a fastball to Gleyber Torres…
…and here he is during his July 5 start in Seattle, his back knee bent slightly more, his shoulders slumped, his glove held a little higher.
Gausman said he made this tweak to get his splitter to move less and therefore look more appealing to hitters. From Matheson again:
(L)ately he’s felt like (the splitter) is “moving a bit too much.” That’s not a problem most pitchers on the planet can even imagine, but the splitter is a different animal.
“I think my mechanics are the reason for that,” Gausman said. “I was getting way too much horizontal movement on my splitter and not enough vertical movement.”
Interestingly, the splitter actually wasn’t all that effective last Saturday; he threw 27 splitters and the Mariners whiffed just twice. Instead, it was the fastball doing damage, even into the late innings of the game.
As a result of Gausman’s mechanical change, the release height on his fastball dropped four inches. Because he was releasing the ball closer to the ground, Gausman needed to aim higher; in mechanical terms, he “flattened” his vertical release angles.1 The easiest way to flatten a vertical release angle is to lower the arm angle, which Gausman told Matheson he did in his Seattle start.
There are two major implications to throwing fastballs with flatter release angles. The first is a drawback — the flatter the release angle, the harder it is to throw a fastball with backspin; therefore, there’s less ride/carry/induced vertical break on the pitch as the release angle flattens. (More on this in an article to come!)
The second is a boon — flatter release angles naturally lead to flatter vertical approach angles, which in turn increases whiff rates, particularly high in the zone.2 Part of why Gausman’s fastball played so well on Saturday is that he managed this tradeoff excellently — he flattened his approach angles while losing just an inch of carry on the fastball.
Lower arm angles (and flatter release angles) are also associated with higher locations. Here are Gausman’s fastball locations in 2024 prior to the Mariners start — note the absence of fastballs thrown high in the zone:
Against the Mariners, the ratio of high fastballs to middle-height fastballs was much better:
After a relatively subtle adjustment, Gausman’s fastball was as effective as it’s ever been. Forget adding a new pitch; with a daring midseason change to his mechanics, Gausman instead found a way back to peak form by rescuing an old pitch.
The average plate height on his four-seam fastballs in his Mariners start was 2.8 feet above the ground; his average vertical release angle (VRA) was -1.7 degrees. In his previous starts, on fastballs thrown 2.75 to 2.85 feet above the ground, his average VRA was -2 degrees. So that’s a 0.3 degree difference, which leads to a corresponding 0.3 degree change in the VAA (4.5 degrees on the former pitches; 4.2 degrees on the latter pitches.)
Both carry and approach angle contribute broadly to “deception,” but it’s hard to have both deceptive factors at the same time, which I go into at some length during my post about Shota Imanaga from May.