HOUSTON (AP) -- Starling Marte insisted he wasn't nervous before his major league debut Thursday night.
When Pittsburgh's prized prospect sent the first pitch he saw into the seats for a home run, it was evident that he was perfectly comfortable in his new role.
Marte's leadoff homer helped the Pirates jump out to an early lead and they held on for a 5-3 win over the Houston Astros.
''I was serious,'' Marte said in Spanish through a translator. ''I was pretty confident.''
Marte is the third player in franchise history to homer in his first at-bat and the first to do it since Don Leppert in 1961. No Pirate has homered on the first pitch of his major league career since Walter Mueller did so in 1922.
A.J. Burnett (12-3) shut out the Astros for seven innings before Chris Johnson and Carlos Corporan connected for solo homers in the eighth to cut the lead to 5-2, bringing Brad Lincoln out of the bullpen with one out.
Johnson hit a two-out RBI single off Joel Hanrahan in the ninth, but Hanrahan struck out Brian Bogusevic for his 30th save.
Pirates fans couldn't wait for Marte, who was recalled from Triple-A Indianapolis, to reach the majors and he didn't disappoint, taking rookie Dallas Keuchel's first pitch deep to left-center.
''I told some players in the dugout before the game that if he threw a fastball down the middle I was going to take a hack at it and that's exactly what I did,'' Marte said.
Keuchel wanted to be more aggressive than he has been and Marte made him pay for it.
''I figured he'd take a strike to see what I got; I never thought he would hit a homer on the first pitch of the game,'' Keuchel said.
Marte was promoted to improve the Pirates' production in left field, where Alex Presley and Drew Sutton have previously manned the position.
Pittsburgh manager Clint Hurdle said he got goose bumps when Marte knocked it out of the park.
''That was a swing that touched a lot of people,'' Hurdle said. ''Starling has been a special player all the way up. He's been a lot of places and a lot of people have had the opportunity to watch him. We've got an entire minor league system and an academy in the Dominican Republic pulling for him. So (it was) really cool, really cool.''
Marte hadn't had a chance to speak to his family in the Dominican Republic when he talked to reporters after the game, but said he planned to send the home run ball to his grandmother there.
The 23-year-old struggled to convey how much Thursday night meant to him and to summarize what a whirlwind the last day has been for him.
''It's a lot,'' he said. ''My emotions are running high right now. It's hard to describe how I'm feeling. It's very emotional.''
Garrett Jones added a two-run homer later in the first inning, and former Astro Clint Barmes had a two-run shot in the second to extend Pittsburgh's lead to 5-0.
The loss runs Houston's skid to a season-worst 10 games and the Astros, who own the league's worst record, have dropped 23 of their last 25 games.
''It's hard coming in every day and getting beat; guys are getting (ticked) off a little bit, and they want to come out here and get a win,'' Johnson said. ''Tomorrow we are going to have to come out here and do whatever we can to get a win. That is what it has to be.''
Burnett allowed four hits and a walk with five strikeouts in 7 1-3 innings to improve to 11-1 since a loss on May 2.
Marte's second hit came on a single to left field in the fifth inning. He hit .286 with 12 homers and 61 RBIs in 98 games this season for Indianapolis.
He said before the game that when his minor league manager called him into the office Wednesday to inform him of his call-up, he tricked him by saying that he didn't run hard enough on a double that day and so he wasn't going to play him in the next game. He then quickly ended the joke by telling him he'd be playing for the Pirates instead.
Marte, who stole 21 bases this season in the minors, was caught stealing to end the fifth inning.
Keuchel (1-3) settled down after the first two innings, allowing just one hit and walking one in his last four innings. He gave up five hits and five runs in six innings.
Burnett didn't allow a hit until Corporan singled to left field with one out in the third. He walked Johnson with one out in the fifth, but didn't allow another hit until Scott Moore singled with one out in the seventh.
Burnett still faced the minimum in that inning after J.D. Martinez grounded into a double play.
NOTES: LHP Wandy Rodriguez, who was traded to Pittsburgh from Houston on Tuesday, will start against his former team Saturday. The Pirates moved starter Kevin Correia to the bullpen to make room in the rotation for Rodriguez. ... Pirates OF Gorkys Hernandez was optioned to Indianapolis to make room on the roster for Marte. ... The teams continue the series on Friday when Pittsburgh's Jeff Karstens opposes Jordan Lyles.