The past week has been filled with controversy cast on pitcher performance, with MLB purportedly set to crack down on foreign substances on the mound. Indeed, the wicked movement on pitches is more gif-able than ever, and the whiffs have provided fertile ground for pitching analysis.
Today, however, I’m more interested in changes to a pitcher’s approach. Think of how hard it is to throw a ball 90 miles per hour. Now imagine you could do that and throw a completely different kind of pitch! Now add two pitches to that!
Pitchers are incredible, is what I’m saying. Some of them add pitches to their already “top .1% of pitches to ever be thrown by virtue of making it to the big leagues alone” in the offseason, and those are some of the pitches we’re looking at today. Here are three pitchers who have added a new look to their repertoire and what that’s meant for them so far.
Each pitcher for this analysis had to throw to at least 50 batters in 2020 and 2021 to qualify for the leaderboard.
Tyler Glasnow, TBR, SP- Slider
Glasnow actually threw a pretty effective slider, at least by results in 2018. It was his third-most thrown pitch (albeit, only 190 times) and generated an incredible 56.5% swing and miss rate while allowing a minuscule .074 batting average and .118 slugging percentage against it.
Then, he shelved it for two seasons. Now, Glasnow is throwing it on almost a third of his pitches, and with a different shape.
The slider in 2018 was breaking vertically 43% more than the average slider, but this year’s breaks just 16% above average. The results on the slider this year have not been in line with 2018’s much more limited sample, at least by the quality of contact:
Tyler Glasnow Sliders, 2018 and 2020
| Year | xBA | xSLG | Whiff% |
| 2018 | .088 | .141 | 56.5 |
| 2021 | .247 | .556 | 46.3 |
The new, tighter slider still has an elite swing and miss rate but possibly keeps hitters off-balance on Glasnow’s four-seamer as compared to last year as the slider increase has mostly come at the expense of his curveball:
Tyler Glasnow Four Seamers, 2020-2021
| Year | xBA | xSLG | Whiff% |
| 2020 | .239 | .465 | 23.9 |
| 2021 | .220 | .381 | 28.6 |
Adding up the more varied arsenal and still-elite whiff rate on the slider has led to a career season thus far for Glasnow, with his lowest-ever xFIP and second-highest strikeout rate of his career, while he’s largely limited walks. The “new” slider is a good one, but it’s the pitch mix that has really been effective for Glasnow in the early going in 2021.
Freddy Peralta, MIL, SP- Changeup
Peralta is in the midst of a true breakout season, through Wednesday sporting a 6-1 record, 2.25 ERA (3.33 xFIP), and striking out more than a third of the batters who have come to face him. The breakout has largely been predicated on his slider, which he debuted after much winter league fanfare in 2020. After throwing it in spring training, Peralta pretty much abandoned it during the shortened 2020 season, but that slider is now nearly equal to his elite fastball in terms of CSW%.
Peralta is no stranger to adding pitches to his repertoire to great success. In 2020, Peralta threw no changeups but has used it for nearly 9% of his pitches thus far in 2021. It should be noted that this isn’t a completely “new” pitch for Peralta, as he did register a few in 2018 and 2019, but those pitch totals (38 and 28, respectively) were so small as to be insignificant or possible misclassifications.
Like Glasnow’s slider, the changeup for Peralta has added a wrinkle that has led to greater effectiveness for his other pitches. The change itself doesn’t have a ton of movement- both its horizontal movement and drop are below average, but it has still generated 35% swing and misses. It’s less than six miles per hour difference from his four-seamer, but his fastball has always been his calling card despite averaging “just” 93 mph. The full arsenal has been effective for Peralta in 2021, and if his change can make the kind of jump in year two that his slider has, he has an even higher ceiling than he’s already reached.
Michael King, NYY, RP- Cutter
In his short 3-year career in the majors, Michael King has relied primarily on his sinker on the mound. Last season across nine appearances, he finished with a 7.76 ERA, and the sinker wasn’t much help, as it generated a .322 batting average against and .508 slugging percentage. Enter the cutter.
After not throwing any in his first two short stints in the majors, King is throwing the cutter nearly a quarter of the time, more than any other pitch except for his sinker, which has dropped from about 60% of all pitches to 50%.
It appears to be a welcome addition, as the cutter has allowed an xWOBA 40 points lower than his sinker this season, and nearly double the rate of swings and misses. It’s added up to a much-improved 3.62 ERA for the Yanks in the early going. King is also seeing less action as a starter, which may be to his benefit up to this point.
The cutter is worth watching though, as if he can pair it effectively with a decent changeup (37.5% whiff rate), it could keep hitters off of that hard sinker.
(Photos by Julian Avram & Dan Sanger /Icon Sportswire | Design by Michael Packard (@designsbypack on Twitter @ IG)