The bullpen used to be a place where failed starters would go to kickstart their career or provide a path for a bounce-back. Mariano Rivera started 10 games for the Yankees in his rookie season. John Smoltz and Derek Lowe had strong seasons as starting pitchers before late-career moves to the bullpen. Edwin Diaz was a starting pitching prospect for three years in the Mariners’ organization before they moved him to the bullpen in Double-A in 2016, and Mason Miller was a talented but oft-injured starting pitcher until the Athletics made him a full-time reliever in 2024.
However, the Miller move is a path that’s becoming more common for young starting pitchers, like Hunter Brown, Garrett Crochet, or Joey Cantillo.
So far, Miller has stayed in the bullpen, unlike the three names I just alluded to, but when the Athletics initially moved him to the bullpen, it was to find a way for him to help their big league team more immediately. It just turned out that he was so dominant out of the bullpen that the team decided to keep him there. Garrett Crochet was similarly dominant out of the bullpen for the White Sox in 2021 and 2023, but he always viewed himself as a starter and is now an ace for the Red Sox.
Using the bullpen as a training ground for young starting pitchers is becoming more common because of the way a bullpen role forces a pitcher to simplify his approach. When I talked to Reid Detmers earlier this month about his move to the bullpen, he stressed that there was no time to mess around in the bullpen: “It’s more of just attacking with my stuff. As a starter, you kind of work around guys, like you’re trying to hit the corners and stuff. Where, in the bullpen, you need to attack.”
Dodgers reliever Ben Casparius, who also spent his minor league career as a starter, told me something similar back in May: “I think the relief side of things has helped with some of my starts too, in just focusing on one pitch at a time and not projecting or looking ahead towards the next inning. It’s just gotten me into a mindset of, every inning, here’s my best stuff.”
That’s a similar mindset that Cleveland Guardians starting pitcher Joey Cantillo adopted this season after pitching his first 28.1 innings out of the bullpen.
“I think the biggest thing that I kind of put upon myself is like, ‘Hey, you don’t have time to settle in,’” he told me during a series against the Mets last week….