Are the Cardinals burning out this key reliever?

The tale of a St. Louis Cardinals' manager burning out a favorite reliever is as old as time. For Mike Matheny, it was Matt Bowman. For Mike Shildt, it was Alex Reyes. In 2022, then-rookie manager Oli Marmol sent out Andre Pallante for over 100 innings.

This year, that trend seems to be continuing. Left-handed reliever JoJo Romero has already pitched in 23 of the team's 47 games. He has thrown 24.2 innings, and he has been used in 4 of the team's last 6 games. In that stretch, Romero has thrown 78 pitches.

All of this is to say that it's possible JoJo Romero is being overused this year. While the decision to pitch or not pitch in a game falls ultimately on the pitcher himself, these are the most competitive people in the world. It's not likely the pitcher will turn down an appearance due to sheer adrenaline. That seems to be the case with Romero.

After Monday night's game, Marmol was asked about Romero's usage. His response was direct.

(JoJo) wants the ball everyday. He loves it. He recovers well. He's resilient, but yes, he's had a heavy workload. Probably threw 104 pitches in 7 days. It's a heavy workload. We'll continue to monitor it.

It is true that Romero is being used frequently and for extended periods at a time. He is tied for 14th in innings pitched by relievers, but most of the players above him have come in relief to pitch multiple innings in low-leverage situations with multiple days of rest in between. Romero being used in high-leverage situations has only added to the mental and physical stress that he's been experiencing.

One stat that displays a reliever's ability to limit damage when he comes into an inning with runners on or shut down a lineup in a new inning is RE24. This stat measures the run expectancy based on 24 base-out states. This website provides more information about this stat. Relievers typically have a higher RE24 than starters, but it's a good measure to see how dominant a reliever can be.

JoJo Romero currently ranks 8th in all of baseball with an RE24 of 8.95. The number is meaningless by and large, but the fact that he's one of the 10 best relievers in baseball according to RE24, win probability added, and other high-leverage statistics prove that he's invaluable to the team. If Romero were to go down with an injury or underperform, the illustrious Cardinal bullpen that has been so dominant could come crumbling down.

Keynan Middleton's imminent return will help alleviate some of the work that has been pinned on not only JoJo Romero but also Andrew Kittredge and Ryan Helsley, but that triumvirate could use additional help.

With Matthew Liberatore likely moving back to the bullpen, and players like John King, Ryan Fernandez, and Kyle Leahy showing an ability to succeed, the bullpen usage will shift slightly as the year goes on. If the offense can continue to improve, then the high-leverage relievers won't be needed as often.