O’Brien emerges as Cardinals’ ninth-inning answer after injury setbacks
Triple-A is a tough place to pitch for a 30-year-old still trying to establish himself as a reliable major leaguer. Development may not be linear, but rarely does it extend so late in a player’s career without some unusual circumstances along the way.
The St. Louis Cardinals didn’t acquire right-handed reliever Riley O’Brien—a trade for cash—until he was nearly 29. While he broke camp with the team in 2024, a flexor strain in his right elbow suffered on Opening Day cost him almost his entire season. When he failed to make the team out of spring training this year, O’Brien suddenly found himself facing those unusual circumstances: trying to prove his health while feeling the pressure of a ticking clock in the background of his career.
“How I felt pitching last year, it felt different than in the past,” O’Brien said. “There was a little more panic, a little more feeling like the game was speeding up on me at times. I talked with Oli [manager Oliver Marmol] this offseason. We had some conversations and really emphasized the mental game. And so far, I think it’s paid off.”
“The stuff has always been real, and the mentality needed to match it,” Marmol said. “I think we’re closing the gap on that, incredibly well, to his credit.”
Prior to arriving in St. Louis, O’Brien had pitched just 2 1/3 innings in the majors, making one appearance each for Cincinnati and Seattle in 2021 and 2022. Once he recovered enough to return to the active roster at the end of last season, he was hit hard; in eight big-league innings, he allowed 10 earned runs on 13 hits. The results weren’t competitive, even if his raw stuff continued to tantalize.
It was enticing enough that the Cardinals held on to him through the winter, remaining open to the idea that he could still be a serious contributor. That gamble has paid off so far; in his first 42 1/3 innings pitched in 2025, he has allowed the same number of earned runs he gave up in less than a fifth as many innings in 2024.
Even that total is somewhat inflated, as it includes the three earned runs he allowed Saturday night in Milwaukee without recording an out. Those three equal the number he allowed in his other 22 outings since July 1, as he seized an opportunity and rose to prominence following the trades of Ryan Helsley, Phil Maton and Steven Matz at this year’s deadline.
“I feel like we redefined the [bullpen] roles as quickly as possible so that it would settle in,” Marmol said. “I felt like we reestablished that pretty quickly after losing those three guys at the deadline, and it’s benefited them. They’ve thrown really well.”
O’Brien now finds himself, at least temporarily, established as the team’s closer, getting a greater share of ninth-inning opportunities in recent weeks than JoJo Romero, with Romero matching up more often against tough left-handed hitters late in games. For a pitcher like O’Brien—whose skills have always shown on a practice mound and under the glare of radar guns—the openings in a seller’s bullpen have presented a world of opportunity that might not have existed otherwise given his career trajectory.
It’s a reminder that development truly isn’t linear, and a demonstration of growth—as well as health and opportunity—unfolding in real time.
“I feel like it’s emphasizing even more how important the mental game is,” he said. “Just sticking with myself, trying not to let too many external factors or anything affect me. Just trying to put myself in the best mental space.”
After Saturday’s blowup put an ugly cherry on top of a rough loss, the team felt urgency in getting O’Brien back on the mound quickly. It was another opportunity to pass another test, and a quick bounce-back would illustrate some of the resilience that’s been in his sights throughout the season.
O’Brien was among the handful of players Marmol sought out after the loss for teachable moments—useful conversations, opportunities seized to prevent disappointment from festering. And it was what O’Brien said in that conversation—which Marmol declined to share—that put him right back on the mound Sunday.
He breezed through four hitters to lock down his fourth save with a one-run lead in the series finale, securing the Cardinals’ only win on a six-game road trip. It was helpful for the team to board a plane with a win at their backs. It was even more meaningful, in their eyes, for O’Brien to see the dividend from his commitment to a process that could see him as one of their lead relievers next season, with more opportunities likely coming.
“I want to see more of that in Riley,” Marmol said. “That’s a big moment for him, to be able to come back the very next day, quick turnaround, and have a pretty clean ending like he just did.”
He’s finishing games, but not his journey. That, against the odds, seems to still be a long way down the road.
This story was originally published September 16, 2025 at 10:17 AM.
