Can the Cardinals Count on Riley O’Brien To Be Their Closer in 2027?

The St. Louis Cardinals had an underwhelming 2026 season, to say the least. They entered the year hoping to scratch their way into the postseason for the first time since 2022 but finished with a 77-85 record, sitting below .500 for just the fourth time since the turn of the century… and the third time within the last four seasons.

The Cards have some very strong pieces on their roster but have struggled to make their success more widespread. This season, they relied heavily on a few major contributors, and this formula simply didn’t work in their favor. Despite having players leading the league in respective offensive and pitching categories, the team’s overall success didn’t come together the way they might’ve hoped.

They have plenty of young star talent on all sides of the ball, and it will be very interesting to see how they approach this upcoming offseason. However, there’s one area in particular where they need to hone their focus. Closing pitcher Riley O’Brien was a first-time All-Star in 2026 but still managed to post some of the most confusing numbers in baseball.

In the second half, he didn’t necessarily look like an All-Star-caliber pitcher, as individual outings and a loss of control resulted in less-than-ideal results on the mound. If St. Louis is aiming to be competitive next season, they need to evaluate whether they can count on O’Brien to be their full-time closer.

A First-Half Surge

O’Brien’s first-half performance in 2026 wasn’t the most incredible stretch, but it was certainly evidence that he deserved to be a full-time closer at the MLB level. During this span, he posted a 3.43 ERA over 37.1 innings, striking out 39 hitters, walking 13, and allowing just two home runs. He also locked down 24 of 28 save opportunities for the Cardinals as the team entered the All-Star break with a 50-44 record.

O’Brien was one of three Cardinals selected to the 2026 NL All-Star team and was the only pitcher from the staff to earn the honor, becoming just the third St. Louis reliever in the last decade to make an All-Star team. He wasn’t the most lockdown reliever in the sense of posting elite strikeout rates or making hitters look silly with every pitch, but he was showing signs of potential.

In 2026, O’Brien’s sinker averaged 97.7 MPH, his sweeper sat at 82.9 MPH, and his slider averaged 90.6 MPH. The main change he made to his arsenal this season compared to 2025 was reversing his usage of the sweeper and slider, his two breaking pitches. In 2025, he threw his slider over 30% of the time, but lowered that usage to just over 7% in 2026.

This change brought him great success in the first half of 2026, carrying over the strong performances from his 2025 season, when he finished with a 2.06 ERA across 42 relief appearances. Through the first half of the season, O’Brien’s 24 saves were the second-most in the National League, behind Mason Miller’s 25, and it looked as though he was on his way to a great season.

The baseball gods didn’t exactly let things play out the way he would’ve hoped, but they didn’t completely tank his season.

Mixed Results in the Second Half

In the All-Star Game, O’Brien pitched a scoreless inning of relief in which he allowed one hit, struck out a batter, and hit Rays star third baseman Junior Caminero in the hand with a fastball, requiring him to leave the game for precautionary reasons. This was unfortunately a sign of the struggles to come in the second half for O’Brien, as he lost his groove following the midseason break.

Across 27 second-half games, O’Brien pitched to a 5.11 ERA with 25 strikeouts across 24.2 innings. His struggles with command became plain to see during this stretch, as he walked 16 hitters, resulting in a 14.4% walk rate.

His second half wasn’t all bad, however, as he carried a 1.42 ERA through his first 14 appearances following the All-Star break. But his season numbers took a massive hit on August 23. Entering to close out the Philadelphia Phillies in a 4-0 game in the ninth inning, O’Brien proceeded to surrender six earned runs, including a walk-off home run at the hands of Kyle Schwarber, earning himself both a loss and a blown save.

His season ERA ballooned from 2.94 to 3.93 in just one appearance, and he pitched to a 4.76 ERA across the 12 appearances that followed this disaster of an outing. If you were to remove the August 23 outing from O’Brien’s season stats, his ERA would drop from 4.08 to 3.23, while his second-half ERA would fall to 2.92 (down from 5.11).

While O’Brien did indeed struggle in the second half of the 2026 season, his numbers were largely inflated by one outlier of an outing. He limited opposing offenses to one or fewer earned runs in 56 of his 66 appearances this season, accounting for about 85% of his games, so he was still a reliable option for the Cardinals in important innings.

Can the Cardinals Count on O’Brien as the Closer?

The St. Louis Cardinals finished the 2026 regular season with a 77-85 record despite having the National League leaders in RBI (Alec Burleson) and saves (O’Brien). They’ll be looking for O’Brien to be a much more reliable back-end option in their bullpen.

The Cardinals don’t have another reliever currently on their roster who boasts the closing potential that O’Brien has, and none are in especially close competition with his pitch mix. O’Brien’s hard sinker does its job by coaxing groundballs at a high rate, but it doesn’t generate many swings and misses. Instead, he relies on his breaking balls to strike out opposing hitters.

O’Brien’s sweeper had the second-highest whiff rate among all sweepers in MLB this season (min. 300 pitches) at a whopping 47.2%. Opponents hit just .138 against the pitch and posted a minuscule .215 slugging percentage, making it by far his most useful offering as a closer. It also has the sixth-most vertical drop of any sweeper and the second-most among relief pitchers.

He has shown over a large sample size that his pitch arsenal can certainly play at the MLB level and produce the results needed to become an All-Star closer. The discourse surrounding O’Brien’s 2026 season often doesn’t fully do his skill set justice, and he should be a reliable closer for the Cardinals next season.

Overall, he was one of multiple Cardinals pitchers who had career-best seasons in 2026 and deserves more credit than his season statistics might indicate. Underneath some of his low moments from this year is a very strong closing pitcher.

Closing Thoughts

While Riley O’Brien wasn’t the most consistent pitcher in the world and had one of the biggest blowup outings of any reliever in baseball this season, that shouldn’t count him out of consideration for the Cardinals’ full-time closer job in 2027 and beyond.

O’Brien became the 29th pitcher in MLB history to blow at least eight saves but still lead his respective league in saves, and just the third pitcher to do so in the last decade. Despite his shortcomings in certain appearances, he’s shown that he can lock down save opportunities at a very high rate.

There may be another level to O’Brien’s game that can be unlocked with a prolonged stint as a full-time closer, and the Cardinals don’t currently have any other pitchers who jump off the page as better closing options than him. He led the National League with 38 saves despite a season filled with varying highs and lows, so who knows what 2027 has in store for him?

St. Louis might not be one of the best teams in baseball at the moment, but it has a strong reliever with the potential to become a multi-time All-Star and one of the most reliable closers in the league.