Boston Red Sox bullpen loading up on lefty relievers in free agency

The Boston Red Sox signed a pair of lefties in free agency

Pitching depth has been a priority for the Boston Red Sox this offseason and their quest to stockpile arms has continued since the lockout ended. The latest moves have been focused on the bullpen, bolstering a strong stable of lefties.

According to FanSided’s Robert Murray, the Red Sox are signing Matt Strahm to a one-year deal. MLB Network’s Jon Heyman reports that the contract is worth $3 million.

Strahm was limited to a mere 6 2/3 innings last year after undergoing patellar knee surgery following the 2020 season. The lefty didn’t make his season debut until August so there isn’t much we can take away from the brief sample as he worked his way back from injury.

Returning to his pre-surgery form would make Strahm an appealing addition. In 2020, the lefty posted a 2.61 ERA in 19 relief appearances.

2019 was an uneven season as Strahm bounced between the rotation and bullpen but he performed much better in relief, which is the role the Red Sox presumably have targeted him for. His best season was 2018 when he posted a 2.05 ERA in 61 1/3 innings (41 appearances, five starts). He held opposing hitters to a .178 batting average that season.

Strahm’s strikeout rate has dropped dramatically in the last two years but that has coincided with improved control. He walked only one batter in his six appearances last year and produced a 1.7 BB/9 in each of the previous two seasons.

Boston wasn’t done building bullpen depth though. According to MassLive’s Chris Cotillo, the Red Sox are signing Jake Diekman to a multi-year deal.

Diekman posted a 3.86 ERA, .211 batting average against and 1.34 WHIP in 67 relief outings (60 2/3 innings) for the Oakland A’s last year. He had a 31.7% strikeout rate last year, which was the fourth highest among left-handed relievers (min. 50 innings). His Whiff% rated in the 96th percentile, per Baseball Savant.

While he’s capable of blowing hitters away at an elite level, Diekman’s spotty command is a glaring warning flag. His 5.0 BB/9 last season matched his career rate and his 13.0 BB% placed him in the seventh percentile. He’s been in the bottom-seven percent of the league or worse in six of the last seven seasons.

Diekman leans heavily on his 95 mph four-seam fastball. He mixes in a hard sinker that can maintain a similar mid-90s velocity and a wipeout slider that held opposing hitters to a .121 batting average last season while producing a 47.0 Whiff%.

With these two signings, the Red Sox add a pair of lefties with different skill sets. Diekman is an elite strikeout pitcher with some control issues and Strahm provides stellar command while pitching to weak contact.

Along with Josh Taylor, Darwinzon Hernandez and Austin Davis, the Red Sox will have no shortage of lefties to call upon from their bullpen. While the trio of lefty relievers returning from last season’s roster have shown wide splits in their careers, the pair of newcomers have shown the ability to produce against hitters from either side of the plate.

MLB has discussed the possibility of using expanded rosters early in the season to offset concerns of as shortened spring training. If the starting rotation hasn’t had sufficient time to ramp up to a full workload, bullpen depth will be vital to navigating the early schedule. With that in mind, the Red Sox might not be done fortifying their bullpen.