Sleeper reliever could become a go-to guy in a Cardinals bullpen full of question marks

The starting rotation for the St. Louis Cardinals has undergone some big changes as Andre Pallante leads the staff in experience. Chaim Bloom has been cognizant of that reality in his first offseason, signing veteran Dustin May and trading for other major league capable arms. With all of the focus being put on the starting staff, the bullpen has mainly gone untouched outside of bringing in veteran Ryne Stanek.

Riley O'Brien could be forced into high-leverage roles for an inexperienced Cardinals bullpen

The current backend of the St. Louis bullpen has lefty JoJo Romero penciled in as closer with standout rookie Matt Svanson behind him, looking to build off a phenomenal first season. Romero, though, has been a rumored trade candidate dating back to last season, but Bloom has yet to find a deal up to his liking. With only one year remaining on his contract and a proven ability to pitch in late-game situations, one would think the interest level in Romero is high around the league. Romero's cheap salary ($4.26 million) and ability to throw left-handed would typically mean the St. Louis phone would be ringing off the hook, but the Cardinals' decision maker has said he is not looking to rush into a trade and is happy to have Romero in St. Louis to start the year.

With injuries and regression always a possibility with relievers, the waiting game is a risky one to play as the Cardinals prepare to head to Spring Training. I would still anticipate Romero to be traded at some point this year, preferably before Opening Day. The gray area around his roster status makes it difficult to envision what Bloom, manager Oli Marmol, and pitching coach Dusty Black have planned for the bullpen.

Romero is currently the lone lefty in the major league bullpen, with Nick Raquet, Justin Bruihl, rehabbing Cooper Hjerpe, and 2025 Minor League Pitcher of the Year Brycen Mautz as the only other southpaws on the 40-man roster. That lack of depth is reason enough to hold onto Romero, but in a rebuild, he is likely more valuable in high-leverage spots for contenders instead of closing out 20 wins for the Cardinals. If and when Romero is dealt, that leaves the closer spot and other late-inning opportunities open for the taking.

A prime candidate to fill into that spot, especially with Kyle Leahy's anticipated move to the rotation, would be Riley O'Brien, my choice last year for the Cardinals' breakout reliever. While he pitched in the most games of his major league career, injuries still hampered O'Brien as he looked to gain traction for a permanent role out of the bullpen. He has a bit of an uphill battle to get there, but if Romero were to be dealt, that ladder to climb gets significantly shorter. In front of O'Brien sits Matt Svanson, who I compared to Kyle Leahy from last year when determining which role is best for Svanson in 2026. After a spectacular debut campaign in 2025, he could easily be put into the closer role, a job he held with success in the minors, or take Leahy's firefighter job and be called upon in any inning and any situation.

Because of Marmol's confidence in Svanson, I see more of the Leahy role for him next season, allowing for O'Brien to come into a more defined late-inning role. In order to grab hold of that job, though, O'Brien will have to unlock a new level of command to go with his electric stuff. For his career, the righty has a walk rate over 13%, which he pairs with a 22.8% strikeout rate. His average fastball sits at 98mph, and his breaking stuff profiles well, but he needs to remain consistent in the zone to be effective in high-leverage spots. Assuming he is coming into camp fully healthy, O'Brien has an inside track at some role in the bullpen, which could evolve into something more permanent with that improved command.

O'Brien is planning to play for Team Korea in the upcoming World Baseball Classic, so the Cardinals will be sure to keep an eye on his usage during the tournament, while also getting a glimpse at what he can do in pressure spots, rather than on the back fields of camp.