Breaking down the 2026 Red Sox postseason bullpen

Garrett Whitlock: 51 G, 49 ⅔ IP, 7-1, 3 SV, 1.81 ERA, 0.83 WHIP, 27.4% K-BB, 25 SD, 5 MD

Only five pitchers in MLB (min: 40 IP) have a better K-BB% than Whitlock’s 27.4%. Those pitchers are Mason Miller, Jacob Misiorowski, Jhoan Duran, Josh Hader, and Mason Montgomery. Four of those guys are elite closers, and one is cruising to a Cy Young Award. Whitlock would have no issue taking over the closer role in 2027, however unlikely that may be.

Erik Miller: 53 G, 47 ⅓ IP, 4-0, 4 SV, 2.28 ERA, 1.31 WHIP, 19.6% K-BB, 20 SD, 7 MD

(With Boston: 15 G, 14 ⅔ IP, 2-0, 1.23 ERA, 1.16 WHIP, 27.4% K-BB, 9 SD, 1 MD)

Speaking of K-BB, Miller was 16.2% with San Francisco and is 27.4% with Boston (identical to Whitlock’s). Lefties are hitting .173 and slugging .247 against Miller in 2026. By the way, Marcelo Mayer has not yet made an appearance for the Giants as he continues to rehab his injuries.

Tyron Guerrero: 38 G, 38 2/3 IP, 1-2, 3.26 ERA, 1.14 WHIP, 18.2% K-BB, 17 SD, 6 MD

Guerrero was unable to stay in the league beyond 2019 due to a 13.6 career BB%, but has remarkably cut that to 4.4% this season. It’s easy to forget that Guerrero didn’t even make his Red Sox debut until May 22nd of this season. Quickly entering the high-leverage picture, Guerrero has thrown ten games this season on no rest and entered with runners on base eleven times. His current IL stint was likely more about giving him some rest and getting him ready for October than a true shoulder injury.

Between the acquisition of Miller via trade and the emergence of the 35-year-old Guerrero, having four power arms like this at the back of the bullpen is essential for October success, with two throwing from the left side and two from the right side.

Tier 2: Have a spot, if healthy

Garrett Crochet: 6 G, 30 IP, 3-3, 6.30 ERA, 1.47 WHIP, 18.8% K-BB (as a starter)

Crochet threw a 30-pitch bullpen session across two simulated innings at Fenway Park on Tuesday. Chad Tracy said, “Everything went well. That was the most volume he’s had, so we’ll see over the next couple of days how he feels and go from there.”

The Woo Sox season ends this Sunday, so it feels unlikely that he’ll go on a minor league rehab assignment. Personally, I’d feel better about things if Crochet made one relief appearance against the Cubs in the final weekend of the season. Sure, he’s “done crazy things before” and “isn’t Joe Schmoe” but I’d rather avoid a return in the seventh inning on the road at Yankee Stadium in a playoff game, if at all possible.

Justin Slaten

I had every intention of putting Slaten into this tier before the news in the past couple of days. Slaten has a “degenerative” arm issue in the flexor (forearm), which can’t be good news in the short or long term.

Tier 3: Something to Prove

With six relievers in the top two tiers, the Red Sox would have needed to choose three arms from the remaining tiers to make up a 13-man pitching staff. Without Slaten, they’ll need to choose four, most likely from this group of six.

Brayan Bello: 24 G (9 GS), 104 ⅓ IP, 6-7, 1 SV, 4.74 ERA, 1.43 WHIP, 9.6% K-BB, 8 SD, 3 MD

Jovani Moran: 48 G, 64 IP, 2-3, 3.23 ERA, 1.11 WHIP, 14.0% K-BB, 12 SD, 4 MD

Greg Weissert: 60 G, 56 IP, 3-2, 1 SV, 3.54 ERA, 1.27 WHIP, 24.2% K-BB, 13 SD, 10 MD

Alec Gamboa: 18 G, 29 IP, 1-0, 1 SV, 1.24 ERA, 1.03 WHIP, 10.6% K-BB, 2 SD, 0 MD

Wyatt Olds: 11 G, 13 ⅔ IP, 1-0, 1.32 ERA, 1.17 WHIP, 22.4% K-BB, 0 SD, 1 MD

Tanner Houck: Last pitched May 12, 2025

Bello, Gamboa, Olds, and Moran all pitched on Tuesday night while trailing, which gives you a bit of an idea of what their “B” bullpen is right now. There will most likely be four pitchers from this group, and it will unquestionably be a difficult choice. The final 11 games will be a continued tryout for all of these pitchers.

Bello‘s overall numbers are shaky, but in 63 ⅔ innings as a reliever, he has a 1.98 ERA, 1.01 WHIP, and 15.1% K-BB. An absolutely remarkable juxtaposition.

After three poor outings in August, I had Moran on the outside looking in. He was likely overworked and has rebounded in September with five consecutive scoreless outings, totaling 5 ⅔ innings.

Weissert‘s overall numbers are decent, but it’s the meltdowns that stick out, and he has ten of them. Other than Slaten (out of the year), no other reliever on the roster has more than six meltdowns.

Gamboa has been a pleasant surprise. He has started two games as the Opener, ahead of Bello. In recent weeks, he’s moved up the chain in leverage, partially due to injuries in the ‘pen, and partially due to success. Gamboa has given up just one run in 11 outings since returning to the team on 8/12 (16 innings). With Chapman, Miller, and Crochet as likely “locks”, it may come down to Moran vs. Gamboa as the final lefty.

Olds had a lot of trouble throwing strikes at every level of the minor leagues, usually sitting between six to seven walks per nine innings. He got to the Big Leagues and has slashed that to 3.3 walks per nine. The strikeouts have always been there, thanks to a unique arm angle and a 113 Stuff+ rating.

Houck was shaky at the start of his rehab but has locked in since. He threw three innings on Friday, allowing one run, and then struck out the side in an inning of work on Tuesday night.