VIERA, Fla. -- Fernando Martinez's debut with the Astros couldn't have gone any better.

Martinez, an outfielder who was claimed off waivers from the Mets in January, made his first Grapefruit League start for the Astros on Sunday against the Nationals and went 2-for-2 with a three-run homer and a walk as the team's designated hitter.

"I need the opportunity to play a couple of games and maybe they want to see me and how I play in the outfield and how I run the bases," said Martinez, a former top prospect of the Mets whose career has been marred by injury. "I'm working hard every day. It's simple. It's like anything -- just enjoy the game and play hard."

The Astros also got homers on Sunday from catcher Chris Snyder, who belted a solo shot off Nationals pitcher Stephen Strasburg, and left fielder J.D. Martinez, who went 1-for-2 with a three-run blast and a bases-loaded walk en route to four RBIs in his first start of the season.

"I was just trying to see pitches and came up in that spot and was trying to hit the ball," J.D. Martinez said. "[Pitcher Tom Gorzelanny] was just trying to come in and he left it in the middle instead of coming in, and I was able to get to it."

Happ shows ability to adjust on the mound

VIERA, Fla. -- After throwing more than he normally would in the offseason, Astros left-hander J.A. Happ felt he arrived at Spring Training a little ahead of the curve. And Happ's first Grapefruit League outing of the year kept him moving in the right direction.

Happ threw 36 pitches in two innings, allowing three hits, one walk and one run while striking out one batter in Houston's 10-2 win over the Nationals on Sunday. The only run he allowed came when he walked designated hitter Michael Morse in the second inning and then gave up a pair of hits.

Walks were a problem for Happ last year, but he was around the strike zone consistently Sunday.

"You have to make adjustments as quickly as possible out there," Happ said. "Once I fell behind Morse, I slowed myself down to try to throw one in there. You need to keep the same tempo and be aggressive, and I felt I did that after that at-bat."

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Astros catcher Chris Snyder was pleased to see how well Happ pitched in and out of trouble in the second inning.

"It's good to see guys right now get some runners on and get themselves into situations where there's two outs, runners on second and third and they have to battle out of it," he said. "That's good to see. You'd like to say every time out you'd breeze through two innings and hit the pitch count, but actually you get more evaluations on them when they get in those situations. Happ and [Henry] Sosa both were in situations like that and handled themselves well."

Wallace taking hands-on approach at plate

VIERA, Fla. -- Astros infielder Brett Wallace has been working diligently with hitting coach Mike Barnett this spring to get his hands in a better position to hit, as well as making sure he's being more aggressive and not thinking as much.

Wallace, who got off to a quick start last year and wound up in the Minor Leagues in August, is hoping to have a spring like he did in 2011, when he hit .377 with one homer and 18 RBIs, which led the Grapefruit League.

"We talked about at the end of last year trying to go up there and do damage and not worry about seeing pitches and being aggressive and attack," Wallace said. "We worked on minor things as far as gaining more freedom in my hands and being loose in the cage."

The hand action, Wallace says, is the key.

"My hands feel good," he said. "I'm definitely going to try to take that stuff on the field and be aggressive with it. It's a process. I'm changing a few things, obviously. The first couple of days [of games], because it's new, you're definitely going to be hit and miss. I'm feeling better every day and I'm hoping to be able to do more damage."

Worth noting

• None of the Astros' injured players made the trip to Viera, but manager Brad Mills said all were progressing. First baseman Carlos Lee (hamstring) is expected to start Monday, while shortstop Jimmy Paredes (wrist) and Angel Sanchez (back) are hitting off coaches in the batting cage. Catcher Humberto Quintero (back/hip) is a few days away from game action.

• Bench coach Joe Pettini didn't travel with the club to Viera and instead stayed in Kissimmee to work with players who weren't making the trip. Mills said he plans to rotate between Pettini, first-base coach Bobby Meacham and third-base Dave Clark on Grapefruit League road trips, leaving one of them behind to work with players who aren't traveling.