A.J. Puk finds immediate sweeping success with Marlins

Miami Marlins manager Skip Schumaker was reluctant to name a conventional closer coming out of Spring Training. The way he spun it was, “we will use our best guys against their best hitters.” Reading between the lines, the real message was, “we’re unsure if any of our relievers can be consistent in high-leverage situations.”

A.J. Puk has quickly made himself Skip’s go-to guy. Puk has finished the game in all seven of his Marlins regular season appearances, including three converted saves. Since Pete Alonso took him deep in his 2023 debut, the tall left-hander hasn’t allowed any other extra-base hits. By win probability added, Puk is among the most valuable relievers in the majors so far.

When the ballpark operations staff coordinates a customized lights show for your entrance from the bullpen, you know it’s serious.

The oft-injured Puk finally established himself as a productive major leaguer with the Oakland Athletics last season (3.12 ERA, 3.69 FIP, 0.3 fWAR in 66.1 IP). The Marlins believed that was sustainable and were intrigued enough to trade for him even though it meant parting with former first-round draft pick JJ Bleday.

From a distance, Puk looks like the same pitcher he was in Oakland. He still throws mid-90s heat. He still gets huge extension off the mound. He still has a nasty breaking ball that he trusts against both lefties and righties.

However, the latter pitch breaks differently than it used to. Puk has modified his slider into a “sweeper” and fallen in love with it.

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This is the first year that Major League Baseball is classifying the sweeper as its own pitch type. There are 76 MLB pitchers who have thrown it in 2023, according to Baseball Savant. Puk is the lone active Marlin on the list—Jeff Lindgren used it liberally in his debut, but he’s now back in the minors.

Last season, Puk’s slider represented 38.1% of his overall pitch mix. This season, his sweeper usage has climbed to 52.5%. He even had a sequence of seven sweepers in a row during Tuesday’s save.

Puk cites former A’s teammate Sam Moll as a strong influence on him.

“Just watching how he throws it and hitters’ reactions, you can kind of see a lot of games going towards it,” Puk told Fish Stripes on Tuesday. “More movement. Harder for the hitters to hit.”

Puk’s sweeper velocity is three miles per hour slower than his old slider, but it gets six additional inches of horizontal break. Opponents expect it drop more than it actually does, causing them to swing underneath it. Corbin Carroll’s well-placed infield single is the only hit against his sweeper so far.

Baseball Savant

Eno Sarris of The Athletic explains that the sweeper’s “big flaw” is its lack of effectiveness against opposite-handed hitters. Puk agreed that it’s “bigger” for him against lefties, but he ended Tuesday’s game by striking out the right-handed David Villar (looking) and Joey Bart (swinging) with his new toy.

Aside from the aforementioned Pete Alonso home run, Puk yielded another (unearned) run when Nick Fortes had trouble receiving this sweeper:

Everybody is still getting acclimated to this sweeping trend. It will be fascinating to see which other Marlins arms try it for themselves, and eventually, what counter-adjustments Puk may have to make once opponents get more familiar with it.