Red Sox Add Corey Kluber to Rotation of Question Marks

Corey Kluber
Ken Blaze-USA TODAY Sports

The 2021 ALCS feels like it happened far more than 15 months ago. After coming within two wins of their fifth World Series berth in the 21st century, the Red Sox dropped 14 wins off their 2021 total to finish in last place in ’22, albeit in the only division in baseball with four teams over .500. The offensive production was okay, the rotation and bullpen proved unreliable, the defense was at times humiliating, and injuries underscored a lack of sufficient depth in a number of areas. Come November, key contributors including Xander Bogaerts, Nathan Eovaldi, and J.D. Martinez hit free agency, leaving Boston with a handful of needs just to stay level in 2023. And though the organization insisted that a Bogaerts extension was its top priority of the offseason, Boston instead watched as the Padres swooped in and inked him to a jaw-dropping 11-year, $280 million deal, leaving the Red Sox with only a fourth-round compensation pick to show for their efforts.

The offseason hasn’t been a total loss. On Wednesday, Carlos Baerga (yes, really) broke the news that the club had signed Rafael Devers to the largest and longest contract in Red Sox history, extending the 26-year-old for $331 million over 11 years. The agreement is a big change of direction for a team that failed to retain either Mookie Betts or Bogaerts, and also a bit of a salvation for a winter that up until last night had seemed to bring more bad news than good.

In terms of bringing on new players to help lift the team back to the playoffs in the immediate future, Boston’s biggest addition this offseason so far is Japanese outfielder Masataka Yoshida on a surprisingly lucrative five-year deal worth $105 million. Beyond him, the Red Sox made some smaller additions on short, low-cost deals for veterans. They aimed to revamp the bullpen with the additions of Kenley Jansen, Chris Martin, and Joely Rodríguez, and brought in Justin Turner as a right-handed corner infield bat and DH. Most recently, they added much-needed depth to the starting rotation by signing 36-year-old Corey Kluber on a one-year, $10 million contract with an $11 million club option for 2024.

Red Sox Major League Acquisitions
Name Pos Age* Proj WAR Years Total Salary AAV
Corey Kluber SP 37 1.6 1 $10.00M $10.00M
Justin Turner 3B/DH 38 1.3 2 $21.70M $10.85M
Chris Martin RP 37 0.7 2 $13.50M $6.75M
Kenley Jansen RP 35 0.3 2 $32.00M $16.00M
Joely Rodríguez RP 31 0.2 1 $2.00M $2.00M
Masataka Yoshida OF 29 5 $90.00M $18.00M
*Denotes age on 6/30/23

Kluber, who has a home in Winchester, Massachusetts, makes sense for Boston in a lot of ways, and indeed the two parties have been pretty frank about their mutual interest over the years. The two-time Cy Young winner has lost some velocity since his prime, but velocity was never his main weapon, and his spin rates remain above average, which helps his pitches retain some of their value. Thanks also to a still-effective cutter, changeup, and curveball, he’s able to entice hitters to chase and produce weak contact as well as ever. In 2022, he finished with 3.0 WAR in 31 starts for the Rays; for context, no Boston pitcher reached 2.0 WAR.

Corey Kluber MLB Percentile Rankings
Year Fastball Velocity Fastball Spin
2015 62 63
2016 54 70
2017 30 84
2018 20 89
2019 14 71
2020
2021 9 62
2022 2 64
SOURCE: Baseball Savant

Kluber also happens to be elite in one facet of the game that sticks out among Boston’s acquisitions this winter. After Red Sox pitching finished 21st in walk rate last season, they appear to be intent on winning the walk battle in 2023. Kluber has allowed fewer than two walks per nine over his whole career; his career-best 1.15 BB/9 rate led all qualifiers last year (among pitchers with 50-plus innings, the leader was Martin at 0.80). Having Chris Sale and James Paxton back in the mix would add two more above-average control pitchers after the losses of Eovaldi and the still un-signed Michael Wacha.

Kluber’s ability to control his pitches was a big part of what made him effective in 2022. He worked the fringes of the zone all year, improving his Edge% from 40.8% in 2021 to 44.3%, good for the 15th-best improvement among 228 qualifying pitchers per Statcast. His called strike percentage also increased, from 16.7% to 18.3%, the ninth-highest rate among major league qualifiers. Outside the zone, he induced a 35.7% chase rate, ranking in the 96th percentile in the league, and in many cases, bad swings led to bad contact. His FB% jumped from 37.9% to 42.0% while his HR/FB rate stayed just about level, and his IFFB% nearly doubled from 9.6% to 17.3%, the second-highest in baseball. Just look at all of these blue dots over the infield and in foul territory:

Last season, thanks in part to more changes to the ball, far fewer fly balls were turning into home runs, helping Kluber transition effectively into a fly ball pitcher. If you’re a pitcher, Boston is a dangerous place for a fly ball — just look at the blue dots again, this time in deep left field — so his ability to keep his HR/FB ratio down after leaving the Trop for Fenway is something to keep an eye on.

Another factor that led to Kluber’s productive 2022 was a change in approach against righties, who went from a .352 wOBA against him in 2021 to a .309 mark in ’22. He ramped up his use of the cutter against same-handed hitters, going from 21.6% to 34.6%, making it his most-used pitch — and it was his most effective, too, at 5.8 runs above average. But he also was able to limit the damage done by right-handers on his sinker by bringing it up and inside instead of trying to beat them down and away with it. Take a look at his sinker usage from 2015 to ’21, during which righties hit .379 with a .423 wOBA and an 89.8 mph average exit velocity on balls in play:

And here it is in 2022, when Kluber held righties to a .304 average and .354 wOBA on balls in play with an average EV of 87.6:

The sinker still wasn’t Kluber’s finest offering, but his ability to push it up and in on righties both limited damage on the pitch itself and opened the door for hitters to chase curveballs and cutters down and away. Here’s a snapshot of all of Kluber’s strikeouts of righties in 2022:

Like many 36-year-olds before him, Kluber did his best in 2022 to refine an arsenal that has lost some of its shine, and the result was enough to get an eight-figure guarantee. But for all Kluber could bring to Boston, his days as an ace are long behind him, and it’s the front of the Red Sox rotation that needs the most attention. Boston didn’t seem to want to play at the top of the free-agent pitching market, missing out on Zach Eflin and Andrew Heaney — two more walk-averse pitchers — to the Rays and Rangers, respectively. Eovaldi joined Heaney in a revamped Texas rotation. Rich Hill, who somehow led the Red Sox in pitching WAR in 2022, wasn’t offered a contract before signing with the Pirates. Wacha could still be an option for Boston; he might be the best arm still available.

For now, Kluber and his two Cy Young awards join a starting rotation full of question marks. Right-hander Nick Pivetta is the only true holdover from the 2022 rotation, and he struggled to find a consistent rhythm last year. Sale’s last three-plus seasons have featured a truly terrible string of luck: Tommy John surgery, a bout of COVID, a fractured rib followed by a non-baseball medical issue, a fractured pinky finger on a comebacker in his second and ultimately final start of last season, and a bicycle accident resulting in a broken wrist. Paxton has yet to make his Red Sox debut after suffering a lat tear during his own Tommy John recovery last summer. After a promising rookie stint in 2022, there’s hope that 23-year-old righty Brayan Bello could earn a rotation spot for years to come, and the Red Sox have told 26-year-olds Garrett Whitlock and Tanner Houck to prepare to join the rotation, though the latter may be more likely to return to the bullpen with Kluber now in the mix.

That’s seven names, and if any five of them are pitching at or near their ceilings in 2023, they could make for a solid rotation. But each comes with his own concerns, and Kluber is the only one with even a 2.5-WAR season in any of the last three years. Red Sox fans will be holding their breath and crossing their fingers for good health.

Red Sox 2023 SP Depth Chart
Name IP K/9 BB/9 HR/9 ERA FIP WAR
Nick Pivetta 178 8.6 3.5 1.4 4.7 4.44 1.4
Corey Kluber 165 7.2 2.1 1.4 4.67 4.36 1.6
Chris Sale 147 10.6 2.5 1 3.47 3.24 2.9
James Paxton 127 8.9 3.1 1.3 4.28 4.11 1.3
Garrett Whitlock 115 8.7 2.6 1.1 4.01 3.78 1.8
Brayan Bello 98 8.7 3.4 0.8 3.89 3.62 1.5
Tanner Houck 26 9.8 3.1 0.9 3.64 3.38 0.5
Kutter Crawford 18 8.9 2.7 1.3 4.23 4.01 0.2
Connor Seabold 18 7.6 2.6 1.5 4.74 4.55 0.1
Bryan Mata 9 8 3.9 1.1 4.52 4.32 0.1
Brandon Walter 9 7.7 2.5 1 4 3.82 0.1
Total 909 8.7 2.8 1.2 4.21 3.97 11.7

Kluber’s signing is somewhat representative of the Red Sox’ additions this offseason. Alone, it’s a sensible move to bring on a useful player to fill a position of need at a reasonable price, much like Turner or Martin or Jansen or Yoshida (though “reasonable price” can always be disputed). But together, the moves still fall short of addressing the team’s needs enough to compete in 2023. The Red Sox are tinkering with a roster that needs more than tinkering, and as it stands now, Boston will need a lot to fall its way to make a run at a playoff spot.





Chris is a data journalist and FanGraphs contributor. Prior to his career in journalism, he worked in baseball media relations for the Chicago Cubs and Boston Red Sox.

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LightenUpFGmember
1 year ago

To add to that last paragraph, Kluber is a guy one adds when their #1-3 starting spots have been taken care of and a veteran, back end guy is what’s needed for innings. If Sale doesn’t show up on opening day, Kluber is arguably the ‘ace’ of this Sox staff. Yeeugh.

Last edited 1 year ago by LightenUpFG
Tony Wisconsin
1 year ago
Reply to  LightenUpFG

I think it’s actually a similar situation. Red Sox have plenty of potential, but they need that potential to have actual opportunity.

You can’t go into the season expecting Sale, Paxton, Bello, Pivetta, and Whitlock/Houck/Winckowski to be good, but they might be. Kluber doesn’t block any of those guys but he’s there to take the place of a question mark if they don’t deliver.

Good signing, clear upgrade over Wacha.