BALTIMORE  — On the day their closest challenger fired its manager, the Houston Astros took their biggest division lead of the season.

Spencer Arrighetti, Ben Gamel and Shay Whitcomb — not exactly Houston’s biggest stars — led the Astros to a 6-0 victory over the Baltimore Orioles on Thursday night. Houston, which just over two months ago was 10 games behind in the AL West, took a 5 1/2-game advantage on Seattle.

“This team finds ways to just stay in the fight,” manager Joe Espada said. “It’s something that has been here since I first got here.”

The Mariners were idle Thursday in the sense that they didn’t play, although they were busy dismissing manager Scott Servais. They may have already missed their best chance to put away the Astros.

After seven straight appearances in the AL Championship Series, Houston was 7-19 early this season. Since then, the Astros are 62-39. Arrighetti, a rookie right-hander, allowed three hits in six innings against the Orioles. Gamel, who was making his Astros’ debut after being claimed off waivers, contributed a pair of RBI singles.

Whitcomb delivered a two-run single in the sixth.

“I give credit to a lot of people. It starts from our front office, and all the way down to player development,” Espada said. “For us to win, we need everyone — and I mean everyone.”

It was the ninth straight road victory for the Astros, and this one came against a Baltimore team that is fighting for first place in the AL East with the New York Yankees — and was pitching Corbin Burnes, its ace.

“As things come down to the wire, it always feels bigger,” Arrighetti said. “I know we’ve got some good amount of games left still, but every time you roll in and you’re playing a team that’s fighting for first in their division while you’re fighting for first in your division, it always feels big.”