VIERA, Fla. -- John Lannan went out and pitched as if he belonged in the Nationals' rotation.
Lannan allowed two hits and two runs over five innings and struck out five and walked one and Washington defeated Houston 7-4 on Monday.
The veteran left-hander trusted his stuff in key situations against the Astros.
"I kind of just gave myself a chance," Lannan said. "I wasn't so hard on myself. I just let (my pitches) work. I tried to throw as many strikes as I could."
Manager Davey Johnson said Lannan will start the season as the team's fifth starter.
While he is in the rotation with Chien-Ming Wang expected to start the season on the disabled list because of a strained left hamstring, there is no guarantee what will happen to Lannan once Wang comes back.
Johnson said Monday he doesn't see Lannan as a reliever right now, which could mean he could be sent to Triple-A, or he could be traded unless another spot in the rotation becomes available.
Lannan was Washington's Opening Day starter in 2009 and 2010 and also led the team in wins last season with 10.
He said he doesn't need Johnson to come give him a pep talk about this situation.
"He doesn't have to worry about me," the 27-year-old said. "There's other things he might have to worry about, but I want him to know he doesn't need to come over here and tap me on the back and say, Hey, it's going to be OK.
"I just don't need that from him. In that case, I think it's better to be left alone, I guess."
Lannan gave up a homer to Houston's Chris Johnson in the second inning.
In the fifth inning, Lannan faced a bases-loaded, no-out situation.
After giving up a run on a sacrifice fly. The Astros used a sacrifice bunt by pitcher Jordan Lyles to put runners at second and third.
Lannan then struck out Astros center fielder Brian Bixler to end the inning.
"That last pitch to Bixler, usually I'll try to pump up (and do too much), but this time I kind of like, That's not going to work," Lannan said. "Usually when I pump up, I leave the ball over the plate. I figured 0-2, I could get in there and luckily he swung at it."
Nationals outfielder Roger Bernadina, who has been working on his swing with hitting coach Rick Eckstein, homered for the second straight day for Washington. His two-run shot in the fifth inning gave Washington a 6-2 lead.
"He felt his command was good," Astros manager Brad Mills said. "I liked the way he mixed his pitches. I liked the velocity he had on his fastball. I thought it might be the best velocity we had.
"I thought he noticeably started to get a little tired there at the end. It's the highest pitch count he's had. He got up to 88, and it was nice to see him be able to get up that high."
Left-handed prospect Kevin Chapman, acquired in a March 20 trade with Kansas City, made his debut for the Astros on Monday and only faced two batters.
Unfortunately for him, the first was Bernadina, who hit the two-run homer.
Offensively for Houston, Brandon Barnes had two hits, including his first home run of the spring off Washington reliever Ross Detwiler. Johnson's home run was his fourth.
Adam LaRoche did some running Monday in front of Davey Johnson and head trainer Lee Kuntz. LaRoche, who sprained his left ankle early in camp, has still been experiencing soreness when he tries to run the bases. The first baseman continued to insist if this was the regular season, he could tape his ankle and play. ... Johnson plans to keep Detwiler on the same schedule he was on last year as a long reliever, pitching him once every five days. ... Johnson said Wang reported discomfort in his left calf, which the manager said is normal because he went through the same thing while recovering from a hamstring injury earlier this spring. Johnson said it was nothing to worry about and Wang's calf should feel better in a couple of days. ... Bud Norris is set to pitch Wednesday against Miami for the Astros.