HOUSTON — Sean Manaea left in the fourth inning with another injury, and things went downhill after that for the Oakland Athletics.

Jose Altuve homered, Joe Musgrove and three relievers combined on a four-hitter and the Houston Astros beat Oakland 6-0 on Monday night.

Manaea (5-9) exited with a left rhomboid strain after 3 1/3 innings. He fielded a comebacker from Yulieski Gurriel to start the fourth, then threw one pitch to Marwin Gonzalez before manager Bob Melvin and the trainer headed to the mound. The left-hander was replaced by Chris Smith.

Manaea said he felt the injury for the first time in the second.

“Just halfway through I felt it on the left side of my spine and it kind of shot through to my shoulder area and that’s when I really felt it,” Manaea said. “That next inning just throwing my warmup pitches I couldn’t really warm up.”

The promising rookie was on the disabled list from June 14-28 with a left pronator strain.

Manaea was uncertain whether he would miss his next start. He is listed as day to day.

“Just frustrating from where I’m at,” Manaea said. “Already been on the DL once and to me it just feels like I’m letting everyone down. I hate being hurt and just getting taken out early, especially with a close game like that just bothered me. It is what it is, I just have to make sure going forward I get everything done and try not to have this problem again.”

Melvin said Manaea wanted to stay in, but his velocity was falling, and he didn’t want Manaea trying to pitch around the injury.

Manaea allowed two unearned runs, one hit and two walks with four strikeouts.

“We walked a couple of guys with the bases loaded but we didn’t do him any favors in the field, could have been out of the inning,” Melvin said. “I thought he was pitching fine. Looked like he had good life on his heater and his slider’s been good and his changeup. Just didn’t do him any favors.”

Marcus Semien had two of Oakland’s hits.

Musgrove (2-2) struck out seven, walked three and allowed three hits over 5 1/3 innings, and then Luke Gregerson, Pat Neshek and Brad Peacock closed things out. Musgrove had allowed 13 runs over his last two starts.

Houston closed within two games of the second AL wild card with the win and Baltimore’s loss.

Altuve hit his second homer in two games to lead off the sixth and extend Houston’s lead to 3-0. Alex Bregman hit a two-run single and Carlos Correa had an RBI single as part of a three-run seventh.

Musgrove retired 11 of the first 13 batters before Khris Davis singled with two outs in the fourth for the first hit against him.

TRAINING ROOM

Athletics: INF Billy Butler was reinstated from the seven-day concussion list. To make room on the roster, INF Arismendy Alcantara was optioned to Class A Stockton. … LHP Sean Doolittle (left shoulder strain) will continue a rehab assignment Tuesday with Triple-A Nashville. … RHP Henderson Alvarez (right shoulder surgery) is set to start a rehab assignment Tuesday in Stockton. … RHP Jesse Hahn (right shoulder strain) will pitch Wednesday for Nashville.

UP NEXT

Athletics: RHP Kendall Graveman (10-8, 3.97) starts Tuesday in the second of the three-game series with the Astros. Graveman is 3-1 with a 1.88 ERA over his last four starts.

Astros: RHP Collin McHugh (8-10, 5.01) will take the mound Tuesday, looking for his second straight win after snapping a four-game losing streak Wednesday in Pittsburgh.