"I felt comfortable there," McCullers said of his reliance on the curve. "I'm a big fastball-curveball guy, and I'll mix in a changeup when I see fit or when [catcher Brian McCann] feels strong about it or calls it. As time moves on, I would like to mix in the changeup more and throw more heaters, but when I get in jams or I need early outs, I feel like I can get that done with my curveball and it's hard to work away from that."
• McCann quickly in sync with Astros' arms
The Mariners were held without a run for their first 12 2/3 innings of the season before Mitch Haniger led off the fourth with a double and scored on an infield hit by Danny Valencia. Three of the five hits McCullers allowed were infield hits.
"He was mixing a lot, trying to keep guys off-balance," Haniger said. "It was working for him a little bit. We just missed some opportunities with runners on base."
The bad luck on some batted balls is nothing new for McCullers, whose actual OPS allowed (.736) last year was 95 points higher than his estimated OPS (.641), according to Statcast™. That was the fourth-largest difference in 2016 among pitchers who faced at least 350 batters.
"He's got the escape ability to get out of these jams with his breaking ball and even some of his fastballs," Astros manager A.J. Hinch said. "He can mix in a few changeups. He got nickeled and dimed a little bit with some infield hits, a chopper here and a mishit here, and still maintained course and was able to get through those three innings."
Mariners manager Scott Servais offered no excuses for his team's early offensive struggles. Seattle was shut out in Monday's season opener, which included seven stellar innings from Dallas Keuchel.
"They ran really good pitching at us the last two nights," Servais said. "Obviously, Keuchel was on top of his game, McCullers has as good of stuff as anybody in the league. You know those are going to be tough right out of the chute."
Brian McTaggart has covered the Astros since 2004, and for MLB.com since 2009. Follow @brianmctaggart on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.