Red Sox Add Walker Buehler to Talented, Risk-Filled Rotation

With their trade for Garrett Crochet back in early December, the Red Sox indicated their intention to aggressively compete for the AL East crown in 2025. The Yankees missing out on Juan Soto, along with the relative inaction of the Orioles and Blue Jays this offseason, has opened that window for Boston. And the Sox have continued to add talent to their pitching staff, signing Walker Buehler to a one-year deal two days before Christmas. The contract will guarantee Buehler $21.05 million, which also happens to be the exact value of the qualifying offer the Red Sox extended to Nick Pivetta and that the Dodgers declined to offer to Buehler. There’s also a $25 million mutual option for 2026 and as much as $2.5 million in performance bonuses for hitting games started thresholds.

After undergoing his second Tommy John surgery in 2022, Buehler finally returned to a major league mound last May, but he really struggled to find his footing after being sidelined for nearly two full years. A June hip injury limited him to just 16 starts and 75.1 innings, and his 5.38 ERA and 5.54 FIP were easily the worst marks of his career. Despite his summer scuffles, Buehler managed to turn things around during the playoffs. He pitched to a 3.60 ERA across 15 postseason innings, including a gutsy scoreless start in Game 3 of the World Series and the first save of his career in the decisive Game 5.

Of course, Buehler was one of the most successful young starters in baseball from 2018–21. Among all qualified pitchers during that stretch, he ranked seventh in WAR, sixth in ERA-, and eighth in FIP-. But postseason heroics aside, 2024 was a pretty miserable year for Buehler. He couldn’t find consistency with his mechanics, and that hip injury seemed to disrupt any progress he was making on that front. He was marginally better after returning from the IL in August and he was able to make a few key adjustments to his mechanics down the stretch — no doubt helping him find some limited success in October — but he entered this offseason as an enigmatic free agent. His early career success was undeniable, but his injury history and disappointing return raised a lot of questions about his ability to contribute quality innings moving forward.

At the core of Buehler’s issues was a four-seam fastball whose quality had deteriorated from elite to merely mediocre. At his peak, Buehler’s heater and its elite ride generated a whiff nearly a quarter of the time a batter offered at it, while also suppressing damage against it when opponents did manage to put it in play. That pitch began to slip in 2022 after the sticky stuff ban went into effect, and a slight dip in his release point — perhaps an advance indicator of the injury he’d sustain midseason that year — led to a sizeable drop in the amount of ride he was generating. His four-seamer didn’t rebound after he returned to the mound after his surgery. Its average velocity sat a tick and a half below where it was in 2019, its whiff rate was a meager 16.9%, and opposing batters produced a .451 xwOBA against it. It’s no surprise that he cut back on his usage of that pitch in favor of a sinker and hard cutter.

Despite its history as an elite pitch, Buehler’s best path forward likely doesn’t involve throwing his heater all that often, and by joining the Red Sox, he might well have sealed that pitch’s fate. With Craig Breslow and Andrew Bailey helming their pitching development lab, the team implemented a staff-wide approach that deemphasized four-seam fastballs in favor of offspeed or breaking pitches. Their philosophy essentially boils down to “stop throwing bad fastballs so much.” That plan likely led to the breakout seasons enjoyed by Tanner Houck and Kutter Crawford and contributed to a much better than expected pitching staff as a whole, though as I’ll discuss later, that breaker-heavy approach might be due for some adjustments of its own given the staff’s second half performance. The Red Sox might push Buehler to drop the usage of that pitch even further than he did in 2024, and thankfully, he has a deep enough repertoire to find a viable mix without it.

Buehler’s one-inning appearance in Game 5 of the World Series could be a preview of what his pitch mix looks like in 2025. He threw 16 pitches in that outing, with 10 of them curveballs and just four of them four-seamers. All three outs were recorded on a breaking ball, and he recorded three whiffs on seven swings against his big breaker. While he won’t be able to get away with such a curveball-heavy mix as a starting pitcher in longer outings, all three of his breaking pitches — a knuckle curve, sweeper, and hard cutter/slider — should see a lot more emphasis with the Red Sox.

For Boston, signing Buehler solidifies a starting rotation that already excelled last year and added Crochet to front the staff. Those two new additions will join a deep group including Houck, Crawford, Brayan Bello, Lucas Giolito, Richard Fitts, Quinn Priester, and Cooper Criswell. Still, their surprising overall success in 2024 hid some concerns that cropped up during the second half of the season. Their starting rotation went from an 85 ERA- and 92 FIP-, fourth and sixth in the majors, respectively, during the first half of the season to a 95 ERA- (12th) and 110 FIP- (22nd) after the All-Star break. Houck and Crawford, in particular, seemed to hit a wall during the dog days of summer. The decline of their starting rotation was a big reason why the Red Sox slipped out of the playoff picture in August and September. The wear from workload increases likely played a part in their second half slump, but it’s also possible the league adjusted to their new approach, necessitating further tinkering in 2025.

Between workload concerns and the recent injury history of many of their starters, the Red Sox have a lot of risk baked into their rotation:

Five of their starters set career highs in innings pitched last year, four added more than 50 innings year-over-year from 2023 to 2024, and seven have lost more than 100 days to the injured list over the last three years. Crochet’s workload and innings limit last year has seen plenty of discussion already and Giolito is returning from an internal brace procedure that wiped out his entire season. Both Houck and Crawford significantly increased their workloads in 2024, and last year was essentially the first time the latter had made it through an entire season without a trip to the IL.

The depth now present in the organization likely buttresses against the attrition that is sure to hit in 2025. Breslow has already hinted at the possibility of using a six-man rotation to guard against some of this risk. That would certainly help alleviate some of the workload concerns, and allow pitchers like Crochet, Buehler, and Giolito, who are each hoping to see significant innings increases in 2025, to pitch into a potential postseason run. The knock-on effect of adding a high-upside guy like Buehler is that guys like Houck, Crawford, and Bello are now slotted into the three, four, and five spots, lessening the pressure on them to lead the rotation. And if everything goes right — if Houck and Crawford pitch like their first-half selves for an entire season, Bello takes a step forward, and Crochet, Buehler, and Giolito remain healthy — Boston could have the makings of one of the best rotations in baseball.

For Buehler, a one-year pillow deal allows him to redefine himself as a pitcher without his trademark four-seam fastball, and do so with the help of one of the more promising pitching development labs in baseball. If he’s able to hone his pitch mix, lean on his breaking balls a little more, and find success with a new approach, he can reenter the market in 2026 looking for a bigger long-term deal. There are a lot of ifs on both sides of the equation here, but this deal looks like a perfect fit.