The Diamondbacks made their first big acquisition ahead of the trade deadline, acquiring left-hander A.J. Puk from the Miami Marlins on Thursday night in exchange for a pair of prospects.

Puk gives the Diamondbacks a second lefty for their bullpen and provides another late-inning option ahead of closer Paul Sewald, joining Ryan Thompson, Kevin Ginkel and Justin Martinez.

Puk, 29, has been a well-known name in baseball circles for more than a decade. Here’s a look at the pitcher the Diamondbacks are getting.

His numbers this year might be misleading

Puk comes to the Diamondbacks with a 4.30 ERA in 44 innings, but those numbers were inflated from the Marlins’ experimenting with him in the rotation early in the season.

In four starts, Puk posted a 9.22 ERA in 13 2/3 innings, walking 17 and striking out 12.

Since being moved back to the bullpen, he has a 2.08 ERA in 30 1/3 innings with six walks and 33 strikeouts.

In 170 career games as a reliever, Puk owns a 3.44 ERA with 216 strikeouts in 178 innings.

Puk also has a track record of shutting down left-handed hitters, holding them to a career .197/.264/.310 line.

A tweak to his pitch mix has keyed his recent run

For most of the first 2 1/2 months of the season, Puk was throwing a sweeper as his primary breaking ball. But after serving up a two-run homer to the Cardinals’ Masyn Wynn on June 17, he ditched the sweeper and went back to his slider, a pitch he used heavily during the 2022 season.

The results have been incredible: He has allowed just one unearned run in 16 2/3 innings since, with three walks and 25 strikeouts.

The slider has been a big part of his success. Since June 19, Puk has allowed just an .059 average off his slider while eliciting a whopping 50 percent whiff rate.

Puk was a highly regarded amateur player

Puk was ranked by Baseball America as the top player on the publication’s draft board ahead of the 2016 draft. He was selected sixth overall out of the University of Florida by the Oakland Athletics.

His career in Oakland was largely sidetracked by injuries. He needed Tommy John surgery in 2018 and missed the entire season. He missed the pandemic-shortened 2020 season with shoulder problems that eventually required a clean-up.

He struggled to put together good results for most of 2021 but emerged in 2022 as a force out of the Athletics’ bullpen, posting a 3.12 ERA in 66 1/3 innings with 76 strikeouts.

Puk was traded last year to the Miami Marlins

Prior to last season, Puk was traded from the A’s to the Marlins in exchange for outfielder J.J. Bleday. It was a swap of highly drafted college players who hadn’t hit their stride with their original teams.

Puk pitched well enough to hold down the Marlins’ closer’s job for much of last year before losing the role to Tanner Scott.

Bleday, meanwhile, had an unimpressive debut year with the Athletics but has been a more dependable option this season, hitting .236/.315/.434 with 12 homers in 102 games.

He had more struggles, injuries this year

Puk, who had long wanted to get a chance to start at the big-league level, struggled in four outings in the rotation to open the year. Not only did he have trouble throwing strikes, he failed to last beyond the fourth inning in three of his starts.

He then landed on the injured list with left shoulder fatigue. He missed only a few weeks before returning to the active roster as a reliever and has since been a highly effective pitcher.

This article originally appeared on Arizona Republic: What to know about new Diamondbacks reliever A.J. Puk