Garrett Whitlock Is More Than Just Aroldis Chapman's Understudy

The Boston Red Sox have made it clear that they are content with their high-leverage set up in the bullpen. They signed Aroldis Chapman to a team-friendly extension in September and have his set-up man, Garrett Whitlock, locked down through the end of this season with club options for both 2027 and 2028. The latter has been incredibly valuable to the organization since he was taken in the 2020 Rule 5 draft; although he’s bounced from the bullpen to the rotation, he’s become an anchor at the end of games the team knows it can depend on.

What those club options likely signal is that Whitlock is waiting in the wings to take over the closer role should Chapman falter or get injured during this season, and more likely once he’s gone in 2027. I’ve long championed for Whitlock to be the closer of the Red Sox but after seeing a handful of All-Star caliber closers sign during the winter, it’s not a far reach to wonder if the Red Sox should have been more involved in that market to help shore up the role through, potentially, the end of the decade.

There’s an injury risk with Whitlock that seems to rear its ugly head on an almost-yearly basis. In 2019, he underwent his first Tommy John surgery that kept him out through the shortened 2020 season. He was healthy in 2021, injured his hip requiring surgery in 2022, was limited by right elbow ulnar neuritis and right elbow inflammation in 2023, strained his oblique in April of 2024, then tore his UCL in May of the same year, requiring an internal bracing procedure. He was then placed permanently in the bullpen for 2025 and he thrived in the role again. It did come out after the season that Whitlock was pitching through a calf injury for most of the second half, but it was never bad enough to require time on the injured list and could be managed with his regular workload. His injury risk should be mitigated as he works out of the bullpen, but it’s something to keep in mind as he’s trusted with more high-leverage spots as the team prepares for a post-Chapman world. 

More importantly, the injury history is about the only negative mark you could give Whitlock. As a reliever, he’s been absolutely dominant on the mound. He proved that there was never a game or situation too big for him when he made his debut with the Red Sox in 2021 and stuck on the big league club for the entire season. Even after his hip surgery in '22, he was rewarded with an extension to keep him around for four more years.

If we look at his numbers from 2025, we can see a pitcher who has finally come into his own and feels comfortable in his late-inning role. He threw 72 innings over 62 games with a 31.1% strikeout percentage, an 8.2% walk rate, a 2.25 ERA, 2.18 FIP, and a  2.2 fWAR. Taking the injury-shortened seasons out, he posted the lowest hard-hit rate of his career at 36.4% and his ERA is the lowest it has been since 2021’s mark of 1.96. On top of all of that, his Baseball Savant page is on fire. Whitlock has proven to be a steady hand as a set-up man and will likely show the same confidence and poise when he transitions to the closer role.

Could the Red Sox have benefitted from signing Edwin Diaz, Devin Williams, or even Ryan Helsley? Absolutely. You can never have too many big time arms at the back of your bullpen. But signing any of them could have hamstrung the finances in a way that may have prevented the trades for Sonny Gray and Willson Contreras or blocked the path to signing free agent Ranger Suarez. Sometimes, you have to trust the arms you have.

This is a situation that bears monitoring going forward, especially if the Red Sox find themselves in a lot of tight games and don't want to burn out Chapman in his age-38 season. A trade deadline blockbuster can't be ruled off the table. But, insofar as he's healthy, Garrett Whitlock has been preparing to take over the closer role since last offseason and will reward the team’s patience with him whenever his number is called.