The St. Louis Cardinals came into the 2026 season with question marks in their bullpen. Trading away players like Ryan Helsley and Phil Maton last season, it was unclear who would be the go-to arms. They went out and made moves this offseason to revamp the pen, adding Ryne Stanek, George Soriano, and Justin Bruihl. The Cardinals
are also relying on Matt Svanson to have a second successful season, in addition to his 2025 campaign. Except for Soriano, the other 3 names have struggled in 2026. The Cardinals’ bullpen is having success in the appearances by Riley O’Brien and JoJo Romero.
Double-Barreled Duo Leads Cardinals’ Bullpen
JoJo Romero
Romero is exactly what the Cardinals are looking for from a lefty out of the bullpen. Lefties are only hitting .133 against Romero. He is also having success against right-handed hitters. Righties also have a sub-300 average against Romero, as they are only hitting .208. Romero made his eleventh appearance on Sunday against the Astros. He finished with 0.2 innings pitched, allowed 2 hits, and 3 earned runs, which were the first earned runs he has given up all season. This was by far his worst outing of the season. Coming into Sunday, Romero’s ERA was 0.00 and is now a modest 2.25.
Although Romero had a rough outing in Sunday’s matchup, he has still been very good for the Cardinals’ bullpen in 2026. In his 11 appearances, Romero has an impressive slash line. He has 12.0 IP, 9 Hits, 6 SO, 3 ER, 4 BB, and a 1.08 WHIP. Romeros’ success is coming from the ability to change speeds effectively. He uses his sinker and sweeper 80.6% of the time, and opponents are only hit .212 off those 2 pitches. He also mixes in a 4-seamer and a changeup. When facing those 2 pitches, hitters are only hitting .062 off Romero. He is also producing a 24.4% chase rate and a 48.5% ground ball rate.
Riley O’Brien
Perhaps one of the biggest bright spots on the Cardinals’ 2026 roster is the emergence of O’Brien. It was unknown who was going to step into the closer role in the Cardinals’ bullpen this season. O’Brien has stepped into that role perfectly. He is a perfect 6/6 in save opportunities and is showing no signs of slowing down. In 12 appearances, O’Brien has 12.1 IP, 5 Hits, 14 SO, 0 ER, 0 BB, and a .41 WHIP. In Sunday’s game against Houston, O’Brien went 1.1 innings, giving up 1 hit, and struck out 2.
O’Brien’s success has come from his ability to be effective out of the zone when needed. O’Brien, just like Romero, relies on his sinker and sweeper 83.4% of the time. Against those 2 pitches, hitters have a .057 batting average. Now, O’Brien finds the strike zone 46% of the time, getting hitters to swing 63% of the time. Playing off his zone consistency, O’Brien isn’t afraid to get hitters to chase outside of the zone with a chase rate of 34.6%. He is also getting ahead in the count early with a 78.4% first-strike percentage.
O’Brien is also having success missing bats in general. Hitters are swinging at nearly half (48.6%) of his pitches, and O’Brien has a 30.4% Whiff rate. And whenever hitters are putting the ball in play, they are hitting the ball on the ground, as O’Brien is currently posting a 75% GB rate.
Back-End Dominance
Every team wants to have a dominant back end of their bullpen to finish games. Between Romero and O’Brien, the duo ranks amongst the top in the Major Leagues. They have a combined 1.13 ERA, 20 SO, 4 BB, and a .75 WHIP. Although O’Brien has all the saves between the 2, it won’t be surprising to see Romero get in on the 9th inning action as well. But as of right now, the Cardinals have won 4 straight, and the double-barreled duo is a major part of it. If their dominance continues, the Cardinals may be set to surprise even more come down the stretch.
Main Photo Credits: Brett Davis-Imagn Images
