Cardinals Has a Potential Arm to Fix MLB's 27th-Ranked Bullpen

Cardinals' Best Start Since 2022 Is Being Undermined by a Broken Bullpen

The St. Louis Cardinals are 21-15 — their most encouraging start in four years — and their bullpen is threatening to waste it. St. Louis ranks 27th in MLB with a 4.87 bullpen ERA, a number that stands out even on a roster that has otherwise looked like a legitimate contender. The Cardinals have a problem. They also, quietly, may have a solution.

That solution is Luis Gastelum, a 24-year-old right-hander currently pitching for Triple-A Memphis. He hasn't made headlines. He probably should.

What Is Gastelum Doing in Triple-A?

In his first Triple-A season, Gastelum has posted a 2.16 ERA across 14 appearances, striking out 14 batters in 16.2 innings for the Memphis Redbirds. Those are legitimate numbers at the highest level of the minors. The engine behind them is his changeup.

MLB.com rates the pitch a 70 on the 20-80 scouting scale — elite grade. It sits in the low 80s, generates -4.9 inches of induced vertical break, and averages 12.9 inches of armside movement. MLB.com prospect analysts Sam Dykstra, Jim Callis, and Jonathan Mayo described it as looking "like a left-handed breaking ball." They went further, suggesting it could one day rival the best changeups in the NL Central.

The results back the scouting. Gastelum's changeup is generating a 25.9% whiff rate this season at Triple-A. Last year at Double-A Springfield, that number was 52%. The dip is expected — Triple-A hitters are better. The pitch still works.

Why Isn't Gastelum Already in St. Louis?

One number explains the hesitation: 12 walks in 16.2 innings. That is not a minor league quirk. That is a significant control problem that would be exposed quickly against major league hitters. A walk rate that high in the big leagues turns manageable situations into crooked numbers.

Gastelum has navigated the walks so far at Triple-A — his ERA proves that. But navigating walks in Memphis and surviving them in St. Louis are different propositions. The Cardinals' bullpen is already bleeding runs. Adding a reliever who issues free passes at this rate is a calculated risk, not a clear upgrade.

The organizational belief in Gastelum is real. The concern about his command is equally real. Both things are true.

What Role Would Gastelum Fill in the Cardinals' Bullpen?

Dykstra, Callis, and Mayo named Gastelum as the Cardinals' future closer candidate in a recent MLB.com column. More immediately, they noted that "many within" the St. Louis organization believe he can contribute at the major league level in 2026. The closer job, however, is not the opening.

Riley O'Brien has that role locked down. The 31-year-old has posted a sub-2.15 ERA with a 0.94 WHIP and double-digit saves in 2026, establishing himself as one of the better closers in the game. St. Louis does not need to replace him.

The need is in the middle innings — the area where the Cardinals' 4.87 ERA is being built. If Gastelum can carry his Triple-A performance into a setup role, he addresses the actual problem. The closer conversation can wait.

How Far Have the Cardinals Fallen — and How Real Is This Turnaround?

The last time the Cardinals were a genuine contender was 2022. That team went 93-69, won the NL Central, and rode Albert Pujols' chase for 700 home runs to one of the most memorable regular seasons in recent franchise history. They lost in the Wild Card round, but the foundation looked solid.

It wasn't. St. Louis went 71-91 in 2023, recovered partially to 83-79 in 2024, then backslid to 78-84 in 2025. Three consecutive non-playoff seasons. A franchise that had made the postseason 11 times between 2000 and 2022 suddenly couldn't sustain a winning record.

The 2026 version at 21-15 looks different. The offense has been more consistent. The rotation has held up. The bullpen remains the one area where the team's record does not reflect its potential. As the source material notes, the Cardinals "could be even better" than their current standing suggests. Fixing the relief corps is the most direct path to finding out.

Is Gastelum the Cardinals' Easiest Path to Bullpen Relief?

The Cardinals have options to address their bullpen externally — trades, waiver claims, free agent signings. But the most cost-efficient answer may already be in Memphis. Gastelum represents the clearest internal path to improving a relief corps that ranks among the worst in baseball.

He has the pitch — the 70-grade changeup that generates whiffs at every level. He has the results — a 2.16 ERA in his first Triple-A exposure. What he does not yet have is the command required to survive in a major league bullpen without inflating pitch counts and putting runners on base.

The question for the Cardinals is straightforward: can Gastelum tighten his control fast enough to help a team that is already in position to compete? If the answer is yes, the call-up writes itself. If not, St. Louis will need to look elsewhere — and the bullpen problem will keep costing them games they should win.

A 21-15 record is a foundation. A 4.87 bullpen ERA is a ceiling. Gastelum is the most promising option the Cardinals have to raise it.