KISSIMMEE, Fla. -- When Bryce Harper came to bat for the first time as a starter in a major league exhibition game, he singled off a pitcher almost twice his age.

Harper, the Washington Nationals' first overall pick in the 2010 draft, singled sharply off Livan Hernandez on Saturday in the second inning of a 3-1 loss to the Houston Astros.

"It's nice being able to start and see different guys and different arms and pitching and things like that," said the 19-year-old Harper, a candidate for Washington's right field job. "Knowing that I'm going to get three at-bats a game is pretty nice. I'm just trying to go up there and not do too much, and trying to get my strikeouts down and my walks up."

Hernandez, who was with the Nationals the last two seasons, is probably going to be in the Astros' rotation and wants to pitch at least three more years.

"I want to be the Jamie Moyer of right-handers," he said.

Harper went 1 for 3, grounding out twice. His first time up against the 37-year-old Hernandez, baseball's active leader in games started (474) and innings pitched (3,121 2/3), provided the kind of learning opportunity that interests the hard-swinging rookie this spring.

"I'm trying to get in work in deep counts -- 0-2 or 2-2, 1-2, things like that," Harper said. "I want to be in those battle counts, just be in that situation and not do too much, drive the ball to the left side and just try to hit off-speed pitches and react to the fastball. If I can see a lot of off-speed and get used to that, it's huge for me."

Harper, who hit .297 with 17 home runs in 109 games in Class A and AA, figures to get a long look this spring, but says it's too early to think about making the team.

"If I play my game and do things right, I've got a shot," he said. "I'm not going to try to do too much and just roll with what I get."

Chris Johnson's two-run home run off losing pitcher Ross Detwiler provided the Astros with their winning margin in the exhibition opener for both teams.

Hernandez and Nationals starter Edwin Jackson pitched two shutout innings each. The win went to Kyle Weiland, the former Boston Red Sox pitcher, who gave up one hit in two shutout innings.

The game marked the return of Astros catcher Jason Castro, who missed the entire 2011 season with a knee injury sustained in the second game of the spring. Castro threw out Jason Michaels easily on a stolen base attempt in the second inning.

"It was nice to get in there and have one of those in the first game," Castro said. "In spring training, guys usually like to run so I was expecting something."

Jed Lowrie, who came from Boston in the same December trade as Weiland, led off the Houston seventh with a triple, leading to their final run.

Doubles by Roger Bernadina and Jesus Flores produced Washington's only run in the fifth inning.