One of the top left-handed pitching prospects is heading to the Major Leagues as the A’s called up A.J. Puk ahead of Tuesday’s series opener against the Yankees.

The A’s No. 2 prospect is expected to work out of the bullpen in his first taste of the big leagues after pitching in relief exclusively at Triple-A Las Vegas. MLB Pipeline has Puk at No. 43 on its overall Top 100 Prospects list, and at No. 5 among left-handed pitchers.

In nine appearances for the Aviators, Puk posted a 4.91 ERA and 0.91 WHIP with 16 strikeouts and three walks in 11 innings, all while holding hitters to a .175 average in the offense-fueled Pacific Coast League.

Selected with the No. 6 overall pick in the 2016 Draft, Puk was poised to impact the A’s rotation in ‘18 before undergoing Tommy John surgery in April and missing the entire season.

The University of Florida product had spent the second part of the previous year in Double-A, earning a midseason promotion to Midland after a standout campaign in the Class A Advanced California League with Modesto. He pitched to a 4.03 ERA and racked up 184 strikeouts in 125 innings (27 games/24 starts) between the two levels, leading all Minor League hurlers with 13.2 strikeouts-per-nine innings.

After a roughly 14-month absence, Puk made his highly anticipated return to the mound on June 11 at Stockton and promptly showed that his pure stuff was still there. He dialed up his fastball to 99 mph in the start, striking out four batters in two innings.

The A’s began to deploy the 24-year-old southpaw as a reliever after promoting him to Double-A in late June, and a subsequent promotion to Triple-A in July made it clear that the organization was grooming him for late-season callup in 2019.

Overall, Puk recorded a 3.98 ERA with 262 strikeouts (12.9 K/9) and 70 walks (3.4 BB/9) in 183 innings across three Minor League seasons.

From a scouting perspective, here’s a preview of what the 6-foot-7, 238-pounder should bring to the table pitching out of Oakland’s bullpen:

Fastball: As previously noted, Puk can really light up the radar gun. He has consistently sat at 96-98 mph while bumping 99 at times this summer, and it’s to fair to wonder whether we might see triple digits from him during some adrenaline-driven appearances in the big leagues. Using his large frame to his advantage, Puk gets excellent extension over his front side that in turn gives his heater late, riding life.

Slider: Puk pairs his nearly elite fastball with one of the best sliders in the Minors. It’s a true putaway pitch -- one that he throws with power at 88-90 mph, with devastating late diving action that nets ugly whiffs from right- and left-handed hitters alike. Puk can adeptly bury it in the dirt when ahead in the count, though his feel for landing it for a strike remains a work in progress.

Changeup: Puk showed the makings of an above-average changeup as a starter, but has largely wiped the pitch from his arsenal this year after it led to some early elbow discomfort. The good news is that Puk really doesn’t need a changeup out of the bullpen given the strength of his fastball-slider pairing.

Control: Puk’s overall control and command leave something to be desired, especially in the wake of his injury, but it doesn’t prevent him from missing bats and generating weak contact from hitters on both sides of the plate. Throwing strikes consistently may be an issue for him at times, but Puk’s raw stuff and natural bat-missing ability should give him a chance to an impact bullpen piece for the A’s.