Red Sox move two-time Cy Young winner to bullpen

The Red Sox are moving struggling veteran Corey Kluber from the starting rotation to the bullpen, manager Alex Cora told hosts Andy Gresh and Christian Fauria in a radio appearance on WEEI Wednesday afternoon (Twitter link). They’ll move back to a five-man rotation consisting of Chris Sale, James Paxton, Garrett Whitlock, Tanner Houck and Brayan Bello for the time being.

Kluber hasn’t made an appearance out of the bullpen since 2013. The 37-year-old signed a one-year deal worth a guaranteed $10M this offseason, with the hope that he’d provide some stable innings to a group that was teeming with injury risk (Sale, Paxton) and young starters who’ll be on innings limits due to lighter workloads in 2022 (Whitlock, Houck). Things haven’t played out that way at all, however.

Through his first nine starts with Boston, Kluber has been tattooed for a 6.26 ERA. His 88.6 mph average fastball is the lowest of his career, and he’s also sporting career-worst marks in strikeout rate (17.7%), walk rate (9.4%) and HR/9 (2.38). He has just one quality start on the year and has only twice recorded an out in the sixth inning. On average, Kluber’s starts have lasted 4 2/3 frames.

Kluber becomes the second member of the Opening Day rotation to slide into a relief role. The performances from Houck and Bello have also displaced Nick Pivetta, who has started more Red Sox games than any pitcher dating back to 2021 and led the team in innings pitched last season.

Houck, 26, has had some rough starts, though the resulting 4.99 ERA is still superior to what Kluber has managed so far. Houck’s most recent outing — six innings, one run, three hits, two walks, eight punchouts — in particular seemed to cement the decision to move Kluber to a relief role. Overall, while Houck’s ERA is only south of 5.00 by the literal narrowest of margins, he’s shown roughly league-average strikeout and walk rates with a strong 51.8% ground-ball rate and a quality 0.92 HR/9 mark. Houck has struggled with men on base, leading to a well below average 61.8% strand rate, but there are plenty of positives in his overall performance.

Bello, 24, has made seven starts and logged a 4.08 ERA through 35 1/3 frames. He’s been slightly better than average in terms of strikeout and walk rate (23.6% and 7.6%, respectively), and his massive 59% ground-ball rate is among the league’s best. Bello has run into problems with the long ball, serving up homers at nearly double the rate of Houck (1.78 HR/9). He’s managed to strand a whopping 81% of his opponents, which will be tough to maintain, but if he can scale back the frequency of his home runs, the strikeout/walk/ground-ball trifecta should allow him to continue finding success.

It should of course be noted that the move to the bullpen for Kluber isn’t necessarily permanent — nor is Pivetta’s shift to a similar role. Both Sale and especially Paxton remain injury risks, and the Sox likely still want to keep an eye on the innings totals of Whitlock (82 1/3 innings in 2022) and Houck (60 innings). As such, it’s quite likely that there will be additional opportunities in the rotation as the season wears on, though whether it’s Pivetta, Kluber, someone from the farm system or an external addition who’s making those appearances will be dependent on how Kluber and Pivetta perform in relief and whether they remain stretched out in multi-inning roles.