Houston rookie Spencer Arrighetti threw six shutout innings and Astros newcomer Ben Gamel had a pair of run-scoring hits in a 6-0 victory against the host Baltimore Orioles on Thursday night.

Shawn Dublin worked two innings and Caleb Ferguson threw in the ninth to complete the combined three-hitter in the opener of a four-game series between American League playoff contenders.

Gamel came through at the plate in his Astros debut. Before Thursday, Gamel — a veteran of more than 700 games — had played in only 24 games across a two-season span. This year, he batted .217 in 18 games with the New York Mets before he was claimed off waivers by the Astros.

The Astros are back on track after losing two of their previous three games. They’ve won 12 of 15 overall.

The Orioles left seven runners on base as they lost for the fifth time in their last seven games.

Arrighetti (6-11) held the Orioles to three hits and one walk with six strikeouts and one walk.

Arrighetti had completed at least five innings in his past seven starts but had only one victory in that span. The Astros were just 1-7 in his last eight games.

Orioles ace Corbin Burnes, the American League starter in the All-Star Game last month, lost his second straight game. He gave up six runs (five earned) on eight hits in 5 2/3 innings with two strikeouts and two walks.

Burnes didn’t allow a hit through the first three innings, but Jose Altuve drew a leadoff walk in the fourth. Altuve scored on Yordan Alvarez’s one-out single before Gamel drove in the second run of the inning with a two-out single.

Gamel provided another two-out, run-scoring single in the sixth as the Astros stretched their lead. Houston went up 4-0 after Jake Meyers’ bunt produced another sixth-inning run. The outburst continued with Shay Whitcomb’s two-run single, putting an end to Burnes’ stint.

Limited to three hits, the Orioles got a first-inning double from Gunnar Henderson and a second-inning double from Ryan Mountcastle, but neither hit resulted in a rally.