Can Garrett Whitlock Rediscover His 2021 Dominance?

Garrett Whitlock is finally back in the bullpen, where he is hoping to return to his best playing days. After the Red Sox selected him in Rule 5 draft in December 2020, Whitlock lit the world on fire in 2021. His appearances became appointment television. It was rare to see a pitcher so young with so much poise, all the more because the Yankees left him unprotected. He appeared in most of the big games that season, and for his efforts he was rewarded with an extension in 2022. But that marked the start of a run of seasons that featured injury after injury. He hit the IL multiple times in 2022 with hip injuries, then again in 2023 with elbow injuries, then again in 2024 with an oblique injury that ended up leading to the UCL injury that forced him to undergo an internal bracing procedure. Now that he’s fully healthy and back in the bullpen, I wanted to look at the start of this season and compare it to the start of his dominant 2021 run to see if we can find any parallels.

To date, Whitlock has thrown 9 2/3 innings with an ERA of 2.79 and eight strikeouts while appearing in six total games. In 2021, during his first six appearances, Whitlock held a flat zero ERA with 18 strikeouts in 13 1/3 innings pitched.  I don’t think those surface-level numbers tell the whole story, though. If we dive in to some more advanced metrics we notice that Whitlock is performing a bit below where he was in 2021. What’s interesting, though, is where some of those differences are coming. So far, he’s underperforming his 2021 numbers in most categories. His chase rate is down a full two points from 29.8% in 2021 to 27.7% so far in 2025, his first-pitch strike rate is down significantly from 64.9% to 56.1%, and his average exit velocity is up from 87.7 mph to 88.5 mph. While those are trending in the wrong direction, his whiff percentage is actually up by a decent margin. In 2021 he posted a 27.6% whiff rate, but so far in 2025 he’s sitting at a 34.2%. The topline results may not be as great, but something is working in his pitch mix.

Until 2025, Whitlock always featured two different fastball looks. From 2021 to 2023, he featured a sinker and a four-seam fastball. In 2024 he replaced the four-seamer with a cutter. So far in 2025, he’s scrapped the secondary fastball altogether and trimmed his pitch mix down to just four pitches: sinker, slider, changeup, and sweeper. With this comes a couple of changes that can explain the uptick in his whiff rate. He’s throwing the sinker harder than he’s thrown it since 2021, currently averaging 95.7 mph. It’s also being thrown with more rise, likely due to him raising his arm slot from 37 degrees in 2021 to 40 degrees in 2025. The increase in velocity is likely causing more hitters to swing and miss on the pitch, but the pitch is being left up in the zone so when it is hit, it’s getting hit harder than ever. 

The other noticeable issue is that Whitlock's sweeper and slider are much closer in average velocity in 2025 than they have been in the past. They're only separated by about two miles per hour this season, where before there was as much as a 4-mph difference between the pitches. His sweeper and slider also have very similar movement patterns this season. Along with the small difference in speed, that means Whitlock either has to dot each type of breaking pitch perfectly, or hitters can sit on one and still hit the other.

As he works his way back from surgery, Whitlock can easily reclaim his title as most dominant bullpen arm in the bullpen. He asked to be moved back to the bullpen and likely realizes that he will be given every opportunity to be successful with the Red Sox. So far, Alex Cora has trusted him in close games and that trust should persist. Should Whitlock be able to improve his command, we’re could be looking at the most dangerous setup man in the big leagues.