The St. Louis Cardinals are still scratching and clawing for a Wild Card spot, but Monday brought a gut punch to their bullpen plans. One of their biggest surprises of the season, right-hander Riley O’Brien, has been shut down “for the time being” after an MRI revealed soreness in his throwing shoulder.
It’s a brutal blow to a team hanging on the edge of the playoff chase with a 68-70 record. The Milwaukee Brewers are long gone with a 17-game lead in the NL Central, so the Wild Card is the only path forward. But losing O’Brien — who has been nails since the trade deadline — makes the climb steeper.
From Afterthought to Breakout Star
If you only looked at his career stats before 2025, you never would’ve guessed O’Brien would become this important. In 10 big league games before this year, he owned a staggering 10.45 ERA. He was a journeyman at best. But something clicked this season in St. Louis.
Across 31 appearances, O’Brien has been lights out: a 2-0 record, 1.69 ERA, 1.13 WHIP, and 35 strikeouts in 37.1 innings. Since Ryan Helsley, Steven Matz, and Phil Maton were traded at the deadline, O’Brien stepped into high-leverage innings and didn’t flinch. In nine post-deadline outings, he posted a 1.74 ERA and kept opposing lineups at bay when the Cardinals needed it most.
“He’s been counted on in high-leverage spots and in closing roles,” MLB.com’s John Denton shared Monday on social media. “This has been a breakout season for O’Brien.”
In fact, some argue that he might be Helsley’s replacement in the 9th inning.
Timing Couldn’t Be Worse
What makes this sting is how little time is left. With just 24 games to play, even a short stint on the Injured List could effectively end his season. Building back up, getting sharp, and returning before the year closes feels like a long shot — though the Cardinals haven’t officially ruled it out.
That said, O’Brien’s performance has already made a strong case for his role in 2026. The Cardinals bullpen, even after losing key arms, still ranks among baseball’s best — and the flame thrower has been a massive reason why. If this is the end of his 2025 story, he’s set himself up as a staple moving forward.
What’s Next for the Cardinals
For now, Oliver Marmol will have to lean even harder on JoJo Romero, Kyle Leahy, and the rest of the relief corps. The bullpen has been this team’s backbone, and without O’Brien’s 100 mph fastball and fearless approach, the margin for error shrinks even more.
Still, there’s optimism around Busch. This was O’Brien’s breakout year, proof that a late bloomer (Riley is 30 years old) can change a career narrative in a hurry. And whether or not he throws another pitch this season, Cardinals fans can already pencil him in as part of the bullpen blueprint for 2026.
One thing is clear: the Cardinals might be on the outside looking in right now, but they’ll head into the offseason knowing Riley O’Brien is no longer a question mark — the flame thrower is now an answer.
