BOSTON -- Just as the Boston Red Sox were beginning to get healthy, one of the best bullpens in baseball suffered yet another blow as the team placed hard-throwing right-hander Tyron Guerrero on the 15-day injured list with right shoulder inflammation on Tuesday. The injury to Guerrero comes just two days after the team activated fellow high-leverage arm Garrett Whitlock from the injured list but still leaves the back end of the Boston pen thin, as the team is already without Justin Slaten, who is still working his way back from right elbow inflammation. 

Guerrero has been a revelation for the Red Sox pitching staff after signing a minor league deal with the club ahead of the 2026 season, posting a 3.26 ERA in 38.2 innings while handling increasingly high-leverage situations as the season wore on. 

With Guerrero joining Slaten on the injured list, these members of the Red Sox have the most pressure on them to perform in their absences: 

Speaking of revelations, that's exactly what the 28-year-old left-hander has been for the Red Sox since being acquired from San Francisco in exchange for Marcelo Mayer ahead of the trade deadline. Miller has allowed only one earned run on eight hits across 11.1 innings of work in a Red Sox uniform, striking out 43.9 percent of the batters he's faced, the fourth-highest rate among relievers with at least 10 innings of work since the Aug. 3 deadline. 

In Guerrero and Slaten's absence, Miller now becomes the primary seventh-inning man as interim manager Chad Tracy looks to bridge the gap between the starter and All-Star closer Aroldis Chapman. 

With two of the three most important right-handers on the shelf, there may not be a single pitcher in the Boston bullpen with more pressure on them to perform than Weissert. For the most part, it's been a rough 2026 campaign for the 31-year-old, as he's posted a 3.83 ERA in 51.1 innings of work. He's particularly struggled when entering games with men already on base, allowing 14 of 34 inherited runners to score, the seventh-most among all relievers. 

After being briefly optioned to Triple-A Worcester on Aug. 7, the 31-year-old has performed well since being recalled on Aug. 13, allowing only two earned runs on six hits in 6.1 innings, allowing only one of five inherited runners to score. 

Managing the Boston bullpen has never been more difficult for the interim manager than it is right now. Without both Slaten and Guerrero out, Tracy has a limited number of right-handed options to choose from in high-leverage spots. Besides Whitlock, Tracy is left with only Weissert and Wyatt Olds, who was recalled after Guerrero was placed on the IL. Playing matchups is now more important than ever for Tracy, who has to more carefully pick his spots, especially when the team is losing, so as not to further burn out his bullpen. 

For much of the season, managing the Red Sox bullpen, which entered action on Tuesday with a 3.14 ERA, the second-lowest mark in baseball, has been straightforward for Tracy, and before him, Alex Cora. Now, Tracy's bullpen managing prowess will be put to the test.