Breaking Down the Boston Bullpen: Part 4

Welcome back to part four of our five-part series examining the 2024 Red Sox bullpen. What did the Sox get from their relievers and what can they expect going forward? The pitchers we’ll be examining today were three of the most make-or-break players in the 2024 'pen.

Kenley Jansen
Kenley Jansen recorded 27 saves in 31 opportunities as the Red Sox closer. Aside from the short 2020 season, that was his lowest save total was his lowest since 2012. However, his 3.29 ERA and 3.00 FIP were both his best since 2021. You'd have to consider his season a success. His 3.01 win probability added ranked 11th among all relievers, and according to Statcast, his trademark cutter was worth seven runs. However, Jansen struggled far more in his age-36 season than he had in any season prior. His 25% chase rate was the worst of his career and one of the worst in baseball, ranking in the 11th percentile. His hard-hit rate, exit velocity, and barrel rate were all the worst he's posted in the Statcast era, and a big reason for his success was that his .253 batting average on balls in play was his second lowest since 2018. 

Jansen just finished a two-year, $32-million deal with the Sox and he seems very unlikely to return. He drew trade rumors after the 2023 season, and for a team attempting to revamp its bullpen, the veteran may not be a fit. He would have to compete with other aging former closers Liam Hendriks and Aroldis Chapman for the job.

Josh Winckowski
Josh Winckowski returned to earth after an incredible and surprising 2023. This past season the righty threw 76 1/3 innings in 40 games with a 4.14 ERA, up from 2.88 in 2023. His underlying numbers got worse too: his whiff rate, strikeout rate, and hard-hit rate all took step back from last season, and all three ranked in the 15th percentile. However, he also suffered from some bad luck, running a very high .337 BABIP, and a very low 61.9% strand rate. So while he definitely fell off in a major way, things might not be quite as bad as they seemed. The biggest difference seemed to be his changeup, which went from saving the Red Sox two runs in 2023 to costing them six in 2024. That's a huge swing, and it makes sense as its hard-hit rate nearly doubled, going from 23.8% to 43.2%.

Winckowski is not yet arbitration eligible, and after all the additions the team has made this offseason, he will likely move down the bullpen pecking order. If nothing else, Winckowski can eat multiple innings out of the 'pen, which could be a big help during a season where multiple starters are on workload limits. If the 2023 version shows up, he could play an important role this season.

Cam Booser
Cam Booser was one of the two left-handed relievers to eat innings in 2024. He ran a 3.38 ERA in 42 2/3 innings as a 32-year-old rookie. His 3.80 FIP wasn't quite so shiny, and his numbers likely got a boost from an 80% strand rate. Booser struggled to keep the ball out of the air. He allowed an average launch angle of 20.6 degrees, among the highest for relievers league-wide. Booser threw three different pitches in his first season: a four-seam fastball, a sweeper, and a cutter. All three pitches graded out as about average according to most pitching models, and all three performed right around the league average as well. Booser won’t be returning to the Red Sox in 2025. He was traded to the White Sox in December for Yhoiker Fajardo. Fajardo is a right-handed pitcher who just finished his age-17 season in the Dominican Summer League, making him more or less a lottery ticket. A league-average arm could really help the White Sox, while Boston's newfound pitching depth means that they have less use for such a piece and might want to take a chance on a talented youngster.

Of our three pitchers, Winckowski will be the only one to don a Red Sox jersey in 2025. Jansen will seek a closing role with another franchise and has mentioned a desire to end his career with the Dodgers, and Cam Booser is doomed to pitch for a White Sox team that may not scratch 60 wins this coming season. We'll return with the final part of our series tomorrow.