BALTIMORE -- Rookie hurler Spencer Arrighetti outdueled All-Star pitcher Corbin Burnes by throwing six scoreless innings to lead the Astros to their ninth consecutive road win, 6-0, over the Orioles on Thursday night at Oriole Park at Camden Yards.

Arrighetti struck out six batters and allowed three hits while walking one batter for Houston, which won for the 12th time in its past 15 games. The Astros have opened up a 5 1/2-game lead over the Mariners in the American League West -- their largest division lead of the season.

Baltimore got one baserunner in each of the first four innings against Arrighetti, who sent down the final eight batters he faced to finish at 94 pitches (60 strikes). Burnes lost to Houston for the second time this season, giving up six runs (five earned) in 5 2/3 innings.

Yordan Alvarez and Ben Gamel -- starting in right field in his Astros debut two days after being claimed off waivers -- both had RBI singles in the fourth. Houston scored four times in the sixth, including another RBI single by Gamel and a two-run single by No. 14 prospect Shay Whitcomb, who picked up the first two RBIs of his career.