JUPITER, Fla. — As the St. Louis Cardinals piece together their Opening Day roster, configuring their bullpen remains a top priority.

Given how instrumental it was to last year’s success, it’s easy to understand why.

The Cardinals hovered around .500 most of last season, eventually clawing their way to an 83-79 record. They did so while posting a minus-47 run differential and one of the slimmest margins of victories in baseball. St. Louis played in 107 games decided by three runs or fewer, posting a .561 winning percentage in those contests. Only the Tampa Bay Rays played in more (109).

Led by Ryan Helsley’s 49 saves and Andrew Kittredge’s 37 holds, the Cardinals consistently locked down games in the late innings. St. Louis relievers combined for a 3.58 ERA last season, the seventh-lowest mark in the majors, and a fourth-best 103 holds. Several pitchers took significant steps forward: Ryan Fernandez impressed in his rookie campaign; JoJo Romero and Matthew Liberatore emerged as legitimate setup men from the left side; and John King solidified himself as a reliable middle-inning option.

Several pitchers — including Helsley — will return to their same roles this season. But the loss of Kittredge in free agency shouldn’t be discounted. In fact, it’s one of the most vital roles the Cardinals need to fill.

They’ll do so internally. Six right-handed relievers — Nick Anderson, Gordon Graceffo, Kyle Leahy, Roddery Muñoz, Riley O’Brien and Chris Roycroft — are competing to round out the bullpen. At least four of eight spots are already claimed: Helsley, Romero, Fernandez and King should be on the Opening Day roster. One of Steven Matz or Liberatore likely needs to be factored in here, as well. Those two are in consideration for starting roles, but the club won’t carry both in the rotation due to their similar profiles. It also won’t carry four left-handed relievers.

How will Cardinals management make its decisions? Performance over the remaining 13 spring training games will matter the most.

“At this point, effectiveness,” manager Oli Marmol said Tuesday. “You want to see them get outs and do what they do. If they’re high ground-ball guys, keep the ball on the ground. If they’re swing-and-miss guys, miss some bats. We’re at that point in camp where performance matters, and we want to make sure that they are the best pieces to move this thing forward.”

Roycroft showed flashes of potential last year after being called up in May. He appeared in 27 games, posting a 4.19 ERA with 33 strikeouts over 34 1/3 innings. He’s yet to allow an earned run this spring and is the top candidate of this group so far. Multiple evaluators within the team consider Roycroft and Muñoz “big arms” with high ceilings, but for different reasons.

Muñoz, a waiver claim from the Miami Marlins in November, was used predominantly as a starting pitcher in 2024. The Cardinals believe Muñoz can unlock some extra force in shorter appearances. Muñoz mixes his five-pitch arsenal (four-seam fastball, sinker, cutter, slider and changeup) pretty evenly, with his fastball sitting just above 95 mph. What will be key for him is establishing which of his pitches are his strongest and utilizing them more effectively.

Graceffo has been a top prospect in the organization since being drafted out of Villanova in 2021. He rose through the Cardinals farm system but struggled to sustain velocity in later innings. The club floated the idea of using him in relief last spring but kept him a starter to help with rotation depth. This year, Graceffo’s stuff isn’t overpowering — his four-seamer sits around 93 mph — but his stuff plays up in shorter stints. That’s what the Cardinals have seen this spring at least, and similar to Muñoz, they’re intrigued about what his arm could develop into as a true reliever, even if the box score hasn’t reflected much success (6.75 ERA through 6 2/3 innings).

O’Brien and Leahy were used sparingly throughout last season. O’Brien’s analytics are a pitching coach’s dream, but translating that into results is what will matter most for him. Leahy’s stuff doesn’t jump off the page, but he added a sinker over the winter and has pitches to retire both right- and left-handed hitters. Leahy is also easily adaptable to different game scenarios, and the Cardinals have shown an affinity for versatile relievers in the past. The team is hoping Anderson, a non-roster invitee, can find the velocity and vertical break from 2019 and 2020 (pre-Tommy John surgery), when he consistently sat at 95 mph and could keep hitters off-balance with his breaking pitches.

Of course, roster status, depth and options will factor in here, too. For example, if Anderson makes the club, he’ll cost a 40-man roster spot and be due $1.1 million. However, his contract includes an upward mobility clause, which allows players on minor-league deals to gauge interest from other teams while under contract. If another club wants to add Anderson, the Cardinals would need to either add him to their 40-man roster or allow him to join the interested organization. Cardinals brass might feel inclined to keep Anderson solely for the sake of not losing him to another club.

Outside of Anderson, there is plenty of fluidity with minor-league options. Bullpens are always revolving doors, but St. Louis could be even more creative with its operations. O’Brien, Muñoz, Leahy and King all have one option remaining, while Graceffo and Roycroft have two.

The Cardinals opened the spring pledging runway and opportunity for their young players. Since then, they’ve faced fair questioning regarding if said opportunity truly exists. It appears to in the bullpen, an area the club knows will be critical in keeping it in contention. That’s the tricky part in this: The most experimental portion of the roster is also the area that will be under the most scrutiny in close games.

Last year, the Cardinals thrived in those scenarios. This year, they’ll be pressed to see if they can repeat that success with a multitude of new names. Roster cuts are looming, and tough decisions will need to be made soon.