The Boston Red Sox have spent much of this offseason circling the top shelf of the free-agent market, with big names like Alex Bregman and Ketel Marte dominating the conversation. But while the headlines have focused on adding star power to the lineup, there’s still a quieter - but no less important - need lingering in the bullpen: left-handed relief.
Right now, the Red Sox aren’t exactly overflowing with reliable southpaws. Aroldis Chapman is the most recognizable name, but at this stage of his career, he’s not the guy you want matching up with lefties in the sixth or seventh inning.
Beyond him, the only lefty reliever on the roster with any major league experience is Jovani Moran. That’s a thin margin for error.
The organization does have some intriguing arms in the pipeline - Payton Tolle, Connelly Early, and Kyle Harrison come to mind - but all three are being developed as starting pitchers. And given their upside, it makes sense for Boston to keep them on that track rather than fast-tracking them into bullpen roles.
Earlier this offseason, the Red Sox were linked to Seranthony Dominguez and Danny Coulombe, both of whom remain unsigned. There’s still a chance Boston circles back, though they’ll likely face competition from other teams looking to shore up their own bullpens. But there’s another name worth watching - one that won’t move the needle on talk radio but could quietly give Boston the left-handed depth they need: Cam Booser.
Booser, a former Red Sox reliever, is back on the market after a stint with the Chicago White Sox. On the surface, his 5.52 ERA over 31 innings in 2025 doesn’t exactly scream “bullpen solution.” But the deeper metrics tell a more nuanced story - and one that could make him a sneaky pickup for a team like Boston.
Against left-handed hitters, Booser was quietly effective. Southpaws hit just .196 off him last season, and he struck them out at a 29% clip.
That’s not a fluke - it’s the result of a well-executed pitch mix, primarily a four-seam fastball and a sweeper, both of which generated swinging strike rates north of 17%. That kind of whiff rate is elite territory, especially for a reliever who’s not exactly a household name.
The issue for Booser? Command.
He walked over 14% of lefties, which is a tough number to work around. Part of the problem may have stemmed from the White Sox reducing his cutter usage - a pitch that had been a high strike-rate offering during his time in Boston.
While the cutter got hit hard in 2024, he made some shape adjustments in 2025 that helped neutralize contact. If the Red Sox were to bring him back and reintroduce that cutter into his arsenal, there’s a chance the walk rate normalizes and his effectiveness against lefties ticks back up.
Booser’s struggles weren’t limited to walks, though. He had a tough time against right-handed hitters in 2025, a sharp contrast from earlier in his career.
His fastball’s swinging strike rate against righties dropped from 14% to just 7%, and that could be tied to changes in pitch location - specifically, an increased tendency to work the outside part of the plate. He still brings solid velocity, sitting around 95 mph, which is more than enough to be effective in short bursts.
But the margin for error is slim when the swing-and-miss disappears.
It’s also worth remembering how Booser landed in Chicago in the first place. He was traded in December 2024 for Yhoiker Fajardo, a young arm who’s since climbed the prospect rankings and looks like a legitimate piece for the future. That deal didn’t work out in Boston’s favor in the short term, but bringing Booser back on a low-cost deal could help balance the ledger a bit.
No, Booser’s not a headline-grabbing addition. But he’s a lefty with upside, a history with the organization, and the kind of under-the-radar profile that can quietly stabilize a bullpen. For a Red Sox team looking to stretch its dollars while still filling key needs, that might be exactly the kind of move that makes sense.