A's top prospect Jesús Luzardo left Tuesday's Triple-A start after four innings and 45 pitches due to tightness in his left lat muscle. He will be re-evaluated on Wednesday.

Luzardo had been scheduled to pitch six innings and between 80 and 90 pitches for the Las Vegas Aviators. The 21-year-old did look sharp before exiting, limiting the Reno Aces to just one run on two hits, with five strikeouts and no walks. It was Luzardo's fifth minor-league outing this season, including three with Las Vegas, as he recovers from a strained shoulder.

MLB Pipeline ranks Luzardo as the second-best left-handed pitching prospect in all of baseball. Last season, coming off Tommy John surgery, he went 10-5 with a 2.88 ERA and 129 strikeouts in 109 1/3 innings between Triple-A, Double-A, and High-A. He likely would have started the 2019 season in the majors had he not suffered the shoulder injury.

The A's did get some good news on the injury front Tuesday, as closer, Blake Treinen is expected to return from the injured list prior to Wednesday's game against the Twins. Treinen went on the 10-day IL on June 21 with a right shoulder strain.

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After an All-Star season in 2018, Treinen has struggled a bit this year, going 2-2 with a 4.08 ERA and 1.53 WHIP in 30 appearances. He has converted 16 saves in 18 opportunities.


To make room for Treinen on the active roster, Oakland will designate right-hander Aaron Brooks for assignment. Brooks went 2-3 with a 5.01 ERA and 1.25 WHIP in 15 games this season, including six starts.