What's Up With George Kirby's Four-Seam? Grayson Rodriguez Simplifying Mix
George Kirby, Grayson Rodriguez, Sawyer Gipson-Long
Mariners George Kirby has seen some fastball regression against right-handed hitters over his last 6 starts. His swing-miss was up around 45% on his four-seam during his great run between mid-July and mid-August. Since, it’s ticked down to 22% (basically league average) as the xwOBA on contact has jumped 100 points to .487. No real shape or release difference, velo is down ~1 mph, but the pitch picked up a slight amount of carry, so FanGraphs Stuff+ is marginally higher. His usage has also ticked down 10 percentage points in his last 6 starts, implying to me that he’s aware of the struggle the four-seam is having. He’s started throwing right-right splitters at a 10% clip as well.
There’s no dramatic change in four-seam location either, perhaps slightly more elevated than it has been in the past. When you look at xwOBA on the four-seam over his last 6 starts, righties are starting to get to it up-away from them, where they previous hadn’t. Sinker doesn’t seem to be keeping them from diving out over plate to touch the four-seam. Time for a counter? Maybe four-seam up/inside? 🔱
Tigers Sawyer Gispon-Long with a pair of strong starts to his career against sub-par offenses. He’s a right-hander who is pushing 90th percentile extension (>7’) and a release height lower than 92% of four-seam releases in MLB. He’s primarily a sinker, slider, changeup arm to righties, four-seam, changeup, slider to lefties. FanGraphs Stuff+ has the fastball grades as both >130, which is two standard deviations above average (plus-plus). I think it’s overvaluing the four-seamer a bit, as even against poor offenses, the swing-miss was below average and contact quality worse than average. Sinker appears plus in small sample, generating well above-average swing miss and good contact quality. Slider is also playing as plus now on results as well, despite the below-average Stuff+ (95). He’s pretty reminiscent of Reese Olson. Plus secondaries getting results, some lack of a strong approach to left-handed hitters, primarily due to sub-par fastball shape and/or no cutter. For what it’s worth, the Tigers have pumped out a few interesting arms this year, SGL is another.
Orioles Grayson Rodriguez has really leaned on his fastball in his last two outings. 60% usage last start followed by 70% yesterday. Odd thing is that he’s actually lost a tick of velocity on the pitch as well, Stuff+ grade down there slightly possibly due to a marginally lower release height, but the xwOBA on contact in this small two-start sample has been above average with the elevated usage. Location to righties has crept more to the upper third of the zone in these past 2 starts, to lefties he’s pushed the primary location away. Both appear to just be leaning into his natural arm-side miss rather than a conscious change.
Tampa is one of the bottom 5 teams in baseball versus four-seamers above 96 mph so I could buy the elevated usage against them, but the Red Sox are more average. He’s backed off his slider in favor of more curveball as well, the latter he’s thrown 16% over his last two starts. Essentially reducing his repertoire to a four-seam, changeup, curveball mix with a rarely used slider. 🔥