The Boston Red Sox bullpen was one of the better relief corps in the American League for most of 2026. By October, it had become the team’s most glaring problem. That contradiction sits at the center of “The Fenway Rundown’s” annual pitching report card — and it produced some of the sharpest grades of the exercise.
Start with the back end, because it was generally the strongest.
Aroldis Chapman saved 35 of 37 opportunities while posting a 1.92 ERA across 53 appearances. Garrett Whitlock, his eighth-inning setup partner, went even further — a 1.72 ERA and a 59-to-9 strikeout-to-walk ratio before injury shortened his season. Both hosts landed on A grades for both pitchers.
Sean McAdam made the larger case for what Whitlock has become.
“He stands as one of the great acquisitions of the Chaim Bloom era, a guy they claimed on a Rule 5 from the Yankees who’s been truly invaluable in relief and as I said, has become, I think it’s hard to argue this, one of the best setup relievers in baseball the last two years.”
Chapman’s 2026 was slightly less dominant than his historic 2025 campaign — when he went months without surrendering a hit — but McAdam refused to hold that standard against him.
“He was an A plus because you could scarcely be better than a Aroldis Chapman was at his job in 2025, but he was still excellent this year, just not quite as dominant. So a straight A for Aroldis Chapman for me.”
The bullpen’s best story was one nobody saw coming. Tyron Guerrero, who hadn’t appeared in the big leagues in years, showed up throwing triple digits and was effectively automatic for months. His 41-to-8 strikeout-to-walk ratio in 40⅔ innings earned an A-minus from both hosts. McAdam marveled at how quickly preseason skepticism had evaporated.
“No one thought this was going to be ... I’d say for a good chunk of the season he was their third best reliever after Chapman and Whitlock.”
Then there’s the story of why October went sideways.
Justin Slaten entered 2026 with expectations to be a significant middle-inning force. He finished with 31⅓ innings, a 4.60 ERA, and multiple high-leverage meltdowns. Chris Cotillo handed out a D and pointed to a damning statistical footnote.
“To me, I give Justin Slaten a D. It might be harsh, but if you look at it, you know, in terms of pitcher WAR on the Red Sox, which I know, it is what it is, he ranked last out of the 32.”
Erik Miller was the most dramatic case. Acquired at the deadline from San Francisco, he looked like a revelation in August — dominant, precise, seemingly past his longstanding command troubles. Then September arrived. McAdam gave him a D-plus and described the unraveling.
“The trap door opened and he fell through it. Not only did he resort to falling behind and walking guys, but he was also hit around a lot and never more so than in those two games in the wild card series where he took over for starters who probably shouldn’t have been lifted in the first place and made things worse by giving up big base hits, including a home run and then a run scoring single.”
Cotillo went C-minus — slightly more forgiving — but agreed that Miller’s wild card failures defined his season. Getting him right as a reliable left-handed weapon, both hosts noted, is among the more pressing tasks of the offseason.
Boston heads into 2027 with a bullpen that’s mostly intact, mostly under control, and carrying some complicated question marks despite being one of baseball’s better units for most of the year.
Listen to the full episode of grades from “The Fenway Rundown” here.
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