Central STL News

Riley O’Brien has emerged as a reliable late-inning reliever for the St. Louis Cardinals during the 2025 season. Despite being in his fourth year in Major League Baseball, O’Brien retained rookie eligibility and took on an expanded role after the team traded Ryan Helsley to the New York Mets at the trade deadline.

O’Brien played a key part in the Cardinals’ bullpen, posting a 2.06 ERA over 48 innings with 45 strikeouts and earning six saves in nine opportunities. Most of his appearances after the trade deadline came in high-leverage situations late in games.

Cardinals reliever John King described O’Brien’s approach on the mound: “You can see it in his face,” King told MLB.com. “You just see the confidence out there and the willingness to attack.”

O’Brien credited his success to enjoying pressure situations. “That’s always your goal in the bullpen, to throw in those late-inning situations,” he said while speaking to MLB.com in San Francisco. “I’ve really been enjoying it. I feel like it brings out my best stuff.”

His pitching repertoire features a sinker averaging 98 mph and a slider around 90 mph, but it is his curveball that has been most effective, holding hitters to two hits in 34 at-bats this season.

O’Brien also noted improvements linked to increased velocity on his breaking ball: “It seems like once it ticked up a couple miles an hour, I definitely started having more success with it, a little more swing and miss.”

Injuries limited O’Brien’s time on the field last year; he missed much of 2024 due to a forearm strain after making only one appearance early that season.

Cardinals manager Oliver Marmol commented on O’Brien’s progress: “You look at where he was last year to this year, there’s been a lot of growth -- not only in his ability to execute but how he handles pressure and stressful innings,” Marmol said. “When things don’t go his way, [he has] the ability to bounce back.”

O’Brien was originally drafted by Tampa Bay and made stops with Cincinnati and Seattle before joining St. Louis ahead of this season.

Reflecting on recent years, O’Brien said: “I feel like there’s been a lot of highs and lows,” he said. “This season has definitely felt like a high. I feel like things have started to click and I’m hitting my rhythm, so I’m feeling good right now.”

After trading several veteran relievers at midseason, including Helsley, Steven Matz, and Phil Maton—all on expiring contracts—the Cardinals expect O’Brien to play an important role moving forward.

King praised O’Brien’s development over the past year: “The growth that he’s had over the last year has been phenomenal,” King said. “The trust in himself is really apparent, and you’re seeing that. You’re seeing him grow and be more comfortable in those situations.”

O’Brien acknowledged what it means for him to have earned responsibility for closing games: “It’s great to have them trust me,” he said. “Hopefully they continue throwing me in those spots.”