Cardinals Fans Need to Pay Attention to What Riley O'Brien Is Doing

St. Louis Cardinals reliever Riley O'Brien is on an insane run to kick off the 2026 season.

Apr 10, 2026; St. Louis, Missouri, USA; St. Louis Cardinals pitcher Riley O'Brien (61) throws in relief in the ninth inning against the Boston Red Sox at Busch Stadium. Mandatory Credit: Tim Vizer-Imagn Images | Tim Vizer-Imagn Images

The St. Louis Cardinals' bullpen hasn't been great overall so far this season. St. Louis currently has the 25th-ranked bullpen ERA in the league at 5.30.

Despite this fact, the Cardinals actually have one of the top relievers in the league with the club right now in Riley O'Brien and fans need to be paying attention. O'Brien broke out last year as a member of the Cardinals and logged a 2.06 ERA across 42 appearances for the organization. Beforehand, he had only made 10 total appearances in the majors with the Cincinnati Reds, Seattle Mariners and the Cardinals.

O'Brien is healthy and has already made 10 appearances so far this season for St. Louis. On top of that, the veteran righty hasn't allowed an earned run yet this season and also has walked anybody. O'Brien has a 0.00 ERA and an 11-to-0 strikeout-to-walk ratio in 10 1/3 innings pitched to go along with five saves.

The Cardinals Closer Is On A Heater

Apr 8, 2026; Washington, District of Columbia, USA; St. Louis Cardinals relief pitcher Riley O'Brien (61) tosses the ball towards first base for the final out to defeat the Washington Nationals at Nationals Park. Mandatory Credit: Rafael Suanes-Imagn Images | Rafael Suanes-Imagn Images

Those are insane numbers and his advanced metrics back them up. Right now, he's in the 99th percentile in expected ERA, 94th percentile in expected batting average against, 91st percentile in fastball velocity, 99th percentile in average exit velocity, 100th percentile in groundball rate, 97th percentile in walk rate, 94th percentile in hard-hit rate and 78th percentile in strikeout rate.

If Mason Miller of the San Diego Padres wasn't on the insane heater that he's on, O'Brien certainly would be talked about around the league in general more this season. Again, this is a guy who made 10 total appearances in the majors between the 2021 and 2024 seasons. Last year, he thrived in his first big role in the majors. This year, he's showing that the 2025 campaign wasn't a fluke and he actually has found a new gear.

Another thing that is great about O'Brien is the fact that he's under team control through the 2030 season. He's 31 years old and the Cardinals can keep him over the next four seasons without any massive expenses.

He's the club's closer right now and he has lived up to the task. If he can stay healthy and maintain this momentum, the Cardinals may not have to think about the closer position for a long time, which would be another box to check for the club. The Cardinals are in a reset period right now but are 10-8 and have one of the top closers in the National League. This team is making some noise.