Why return to the bullpen has worked for A.J. Puk

MIAMI, FL—Lefty A.J. Puk had already shown that he could be a good reliever at the major league level. Still, he believed he had even more to offer. The Marlins tried him out as a starter, and due to a combination of great spring training performance and injuries to his teammates, Puk earned a rotation spot. However, he struggled once the real games began, posting a 9.22 ERA and 6.29 FIP through four starts while walking more batters than he struck out. Puk landed on the injured list due to left shoulder fatigue and moved back to the bullpen upon returning.

Since then, he's appeared in ten games with a much-improved 2.53 ERA and 2.85 FIP. In nine of those outings, he hasn't allowed an earned run. Puk's last four appearances have been hitless and he's showing the versatility to handle any situation, such as inheriting baserunners and going multiple innings.

"Just kind of getting back into the swing of things that I've done in my whole career," said Puk. "It's a pretty easy transition and I am finally starting to feel better. I changed my mechanics a little bit and getting into a groove."

Puk mostly relied on a fastball/sweeper combo in 2023, but as a starter, he needed to expand his pitch mix. That adjustment indirectly caused a mechanical problem.

"It was one of those things where this year, I raised my arm slot," said Puk. "Really wanted to throw that splitter a lot and my body didn't like that new slot. Going back to the bullpen, I've dropped into a little more of a natural slot for me."

Puk could not locate his pitches with the change in arm slot, leading to the huge increase in his walk rate. Also, his velocity dropped. Puk has gone from averaging 93.3 mph on his four-seamer as a starter in April to 95.6 mph since coming off the IL, which is much closer to his career average.

"I was trying to force something that my body really didn't wanna do," said Puk. "It was causing some issues. Take care of that and then it kinda dropped back down to my arm slot and it gets thrown from a little lower slot."

Puk made his first relief appearance of the season on May 13 and that has been a turning point for the Marlins bullpen overall. Since that date, their 'pen has combined for a 2.45 ERA, 2.91 FIP and 1.2 fWAR (tied for fourth in MLB).