OAKLAND, Calif. -- Left-hander Ross Detwiler pitched eight shutout innings in his return to the major leagues and the Oakland A's defeated the Baltimore Orioles 1-0 on Wednesday night at Oakland Coliseum.

Detwiler (1-0) was called up Wednesday from Triple-A Nashville and made his A's debut and first major-league start since May 14, 2015, with Texas. He gave up six hits, struck out two and walked none.

A's right-hander John Axford pitched a scoreless ninth for his second save of the season.

The A's beat the Orioles (63-50) for the third straight time and will go for the series sweep on Thursday afternoon.

The Orioles, who lead the major leagues with 170 home runs, have scored a combined three runs against the A's in three one-run losses. Baltimore fell out of a tie for first place with Toronto in the American League East and trail by one game.

The A's acquired Detwiler from Cleveland on July 17 for cash in a minor-league deal. He went 4-0 with a 3.86 ERA in four starts, including three starts, for Nashville before filling a void in an A's rotation that has been depleted by injuries.

Detwiler made his 181st career major-league appearance but just his 77th start, the role he prefers. He started 69 times for Washington from 2009 to 2013 but had just seven starts, all with Texas last season, before Wednesday. He made seven relief appearances for Cleveland this season before being designated for assignment.

Yonder Alonso went 2-for-3 with a walk and an RBI double for the A's.

Orioles right-hander Yovani Gallardo (4-4) gave up one run and four hits in six innings. He struck out six, walked two and had third quality start in his past four outings.

The Orioles appeared to take a 1-0 lead in the first inning when Adam Jones singled, moved to second on a wild pitch and was ruled safe in a close play at the plate after J.J. Hardy doubled off the right-field fence. But the A's challenged the call and it was overturned after a video review.

The A's struck first with a run in the third. With two outs, Marcus Semien doubled to deep center field and scored on Alonso's double to the right field corner.

NOTES: A's RHP Patrick Schuster was designated for assignment, opening a spot on the roster for LHP Ross Detwiler, who was called up from Triple-A Nashville and started against Baltimore. ... Orioles OF Steve Pearce (right elbow strain) missed his third straight game Wednesday against Oakland but said he continues making progress and remains confident he'll avoid a trip to the disabled list. ... LHP T.J. McFarland (left knee inflammation) pitched three scoreless, hitless innings Wednesday in a rehab appearance for the Orioles' Gulf Coast League farm team. McFarland struck out one and walked one. He'll make his next outing Monday for Class A Frederick. ... A's minor-league RHP Jharel Cotton threw a one-hitter with 12 strikeouts and no walks for Triple-A Nashville on Tuesday night against Round Rock. He had a perfect game until giving up a triple with one out in the ninth inning. Cotton was one of three minor-league pitchers the A's acquired from the Dodgers in exchange for RF Josh Reddick and LHP Rich Hill on Aug. 1. "He definitely opened some eyes," A's manager Bob Melvin said. "It wouldn't surprise me if at some point in time (this season) we see him here."