With 46 games to play in the regular season, the Red Sox are now a stunning four full games clear of the Texas Rangers and Cleveland Guardians (the first teams out of the playoffs) and have an 75.1% likelihood of making the playoffs, per Fangraphs. While the paths to playing time are clearer within the lineup and the rotation, the bullpen feels like it has quite a bit of variance when it comes to who might be included on a playoff roster.
Let’s take a look at the 16 possible candidates that I could conceivably see pitching in the postseason, breaking them out into five tiers:
The High Leverage armsDeserving of a Postseason spotSomething to ProveLongshotsLooming Prospect Callups
Note: I’m including Shutdowns vs. Meltdowns as “SD” and “MD” in the statline. Fangraphs’ explanation is here.
Ken Blaze-Imagn Images
Aroldis Chapman: 49 G, 44 ? IP, 3-2, 21/23 SV, 1.21 ERA, 0.76 WHIP, 31.0% K-BB, 29 SD, 5 MD
After a 15.4 BB% from 2021-2024, Chapman has cut that exactly in half to 7.7% over 44 ?
? innings with the Red Sox as their capital-C Closer. Absolutely masterful in any and all situations. Chapman is in the top-2 percentile in xERA, xBA, Fastball Velo, Whiff%, and K%. Arguably, one of the three most important players that needs to stay healthy for this team to succeed in the postseason.
Garrett Whitlock: 43 G, 52 ? IP, 5-1, 2.91 ERA, 1.12 WHIP, 21.3% K-BB, 21 SD, 6 MD
The trusted eighth-inning guy, Whitlock looks like 2021 Garrett Whitlock again. He has only allowed a run in three of his past 28 appearances, while 34 of his 43 appearances overall have come in the seventh inning or later. After a 23% K-rate over the past two seasons, Whitlock is putting batters away with a 30.6 K%, which is in the 92nd percentile in baseball.
Justin Wilson: 43 G, 35 IP, 3-1, 2.83 ERA, 1.37 WHIP, 18.2% K-BB, 17 SD, 9 MD
After a shaky first ten appearances as a Red Sox, Wilson has allowed just seven total runs in his past 33 appearances. While it doesn’t always occur in the seventh inning or later, Wilson is typically brought in for the biggest spot in the game that a key left-handed hitter, or stretch of hitters, needs to be shut down. His Whiff% and Hard-Hit% sit in the 90th percentile.
Tier 2 – Deserving of a Spot (if healthy…)
Photo By Winslow Townson/Getty Images
Greg Weissert: 52 G, 48 IP, 4-3, 2.81 ERA, 1.17 WHIP, 10.1% K-BB, 20 SD, 7 MD
You could argue that Weissert deserves to be in the High Leverage tier on the whole, but since July 1, he’s been deployed in the 6th inning in half of his outings, and his K% is in the 21st percentile. Weissert was overused in June, appearing in 15 of the team’s 26 games and understandably hit a bit of a wall late in that month. But he hasn’t given up an earned run in his past 10 appearances and deserves to be back in the Circle of Trust. His 52 appearances are tied for fith in the American League, and only two behind the league leader, Louie Varland.
Justin Slaten (IL-60): 24 G, 23 ? IP, 1-4, 3 SV, 3.47 ERA, 10.0% K-BB, 15 SD, 5 MD
Slaten has been dealing with a nerve issue in his shoulder, which is outlined here, but has been throwing off a mound this week and hopes to be back by the end of August. Slaten was the highest leverage “non-Chapman reliever” through the end of May with 18 of his 24 appearances coming in the eighth inning or later, tallying three saves in the first month of the season. He could easily rejoin the top group with a strong September, but will first need to prove that he’s healthy in an August rehab.
If the five guys above are all in good form, it’s difficult to see any of them not on the roster. If we assume that a rotation shortens to four in the playoffs, then we would need to find four more relievers from the following (long) list for a total of nine. Since rosters expand to 28 players in September, the team would likely carry nine relievers in that month, as well.
Tier 3 – Something to Prove
BOSTON, MASSACHUSETTS – JULY 7: Chris Murphy #72 of the Boston Red Sox reacts during the sixth inning against the Colorado Rockies on July 7, 2025 at Fenway Park in Boston, Massachusetts. (Photo by Maddie Malhotra/Boston Red Sox/Getty Images) Getty Images
Brennan Bernardino: 47 G, 43 ? IP, 4-2, 3.09 ERA, 1.26 WHIP, 7.3% K-BB, 6 SD, 7 MD
Would have been in Tier 2 a week ago, but his recent demotion and a 22:36 BB:K ratio this season leave just enough doubt. Bernardino has not pitched since his last MLB outing on July 28 and very well could just be getting a “reset” on an arm that has made 49 appearances (two of which were in the minors) already this season. Bernardino has more meltdowns than shutdown appearances this season, with only 19% of his pitches thrown this season being in high-leverage situations but hitters are batting just .199 against him this season (with a .225 xBA). Bernardino also has an 81st percentile GB%.
Chris Murphy: 12 G, 20 IP, 2-0, 2.25 ERA, 0.80 WHIP, 16.0% K-BB, 3 SD, 0 MD
Bernardino’s demotion may have partially been due to the effectiveness of Murphy in recent weeks. With the exception of the three home runs he allowed at Wrigley Field in mop-up duty, Murphy has been lights out, with nine of his 12 outings being scoreless. He has been asked to get 5+ outs in seven outings and is gaining trust as a long man in the Sox pen.
Steven Matz (STL + BOS): 34 G (2 GS), 57 IP, 5-2, 3.44 ERA, 1.18 WHIP, 16.2% K-BB, 8 SD, 9 MD
Sticking with the lefties theme, Matz has thrown two shutout innings since arriving in Boston. He was excellent for the Cardinals over the first six weeks, but since May 14th, has a 5.04 ERA (3.84 FIP) and a 1.42 WHIP.
Jordan Hicks (SF + BOS): 25 G (9 GS), 59 IP, 1-7, 2 SV, 6.41, 1.59 WHIP, 9.3% K-BB, 1 SD, 6 MD
Hicks has a 6.10 ERA in 10 ?
? IP with Boston thus far, and has 8 BB+HBPs to go with 8 strikeouts. He’s gotten two saves and looked great in those outings, but his struggles have otherwise been an extension of the pitcher that he was in San Francisco. Hicks is in just year two of a 4 year, $44M contract, and was likely just thought of as a way to move salary back to Boston in return for what they were taking on with Rafael Devers.
Cooper Criswell: 7 G (1 GS), 17 ? IP, 1-0, 3.57 ERA, 1.58 WHIP, 5.0% K-BB, 1 SD, 0 MD
Criswell is a depth arm for both the rotation and as a long man out of the bullpen. With a 4.48 career ERA in 154 ?
? innings, he’ll likely throw some more innings that matter in the 2025 regular season. Could easily be a 13th arm in a playoff series, should a game go to extra innings or a starter is forced to exit early.
Photo By Winslow Townson/Getty Images
Kelly was a key piece to the bullpen a year ago and has just recently returned to Worcester from the 15-day IL with an oblique injury. With Boston, Kelly has thrown 22 ?
? IP with a 5.56 ERA (3.64 FIP). If Kelly can find his stuff and throw strikes, it can’t be ruled out that he is back up with the club in September.
He was recalled on Tuesday when Jorge Alcala was DFA’d. Campbell has seven saves and a 4.17 ERA in 45 ?
? IP (34 G) at Worcester and feels like he will only be in Boston temporarily.
A six-year MLB veteran, Burdi has great numbers at Worcester when healthy this season. Over 23 innings, his ERA is 1.96 with 11.7 K/9. He recently returned from foot and hip injuries at Worcester, but did throw 5 ?
? IP for the big club in May of this season without allowing a run.
Guerrero recently shifted to the 60-day IL with an elbow sprain. Although he hasn’t been ruled out for the season, there is no news of throwing yet, and he can’t be relied upon to be available in October.
Never has the release of a pitcher with a 3.31 ERA in 19 appearances ever been more understandable. Last Tuesday, Alcala allowed two runs in ?
? of an inning, forcing the usage of Aroldis Chapman for a one-out save. On Saturday, Alcala allowed two of the three baserunners he faced to reach base, forcing the usage of Aroldis Chapman for a two-out save. This past Monday, Alcala allowed three runs, including two home runs, in ?
? of an inning, forcing the usage of their three highest leverage relievers in an unnecessary 8-5 final. Unnecessarily wear down the closer three times in one week? He gone.
Tier 5 – Prospect Call-Ups
Payton Tolle (MiLB combined numbers): 17 G (15 GS), 4-1, 2.93 ERA, 76 ? IP, 1.02 WHIP, 31.1% K-BB
The 22-year-old Tolle made 11 dominant appearances at High-A to start the season, followed by six appearances at Double-A that were more dominant than the High-A starts, before being promoted to Worcester this week. He has thrown 76 ?
? innings on the season and it’s not inconceivable to think that if the team wants to manage his workload in a few weeks, maybe they shouldn’t waste these bullets in the minor leagues. Tolle, the #1 prospect on Sox Prospects, would need to be added to the 40-man roster before September 1 to be eligible for postseason play. Even if that happened, he would still be eligible for Rookie of the Year incentives in 2026 since he would fall short of the 50-inning and 45-roster day thresholds.
David Sandlin (MiLB combined numbers): 19 G (14 GS), 88 ? IP, 7-4, 3.65 ERA, 1.18 WHIP, 17.9% K-BB
Copy and paste the Tolle paragraph from above, only slightly less dominant. Sandlin is the #9 prospect at Sox Prospects.