PHOENIX -- Alex Cintron took advantage of a rare night in the starting lineup.
Cintron, making his first start at third base and fourth start overall, was 3-for-4 with his second and third RBI of the season.
"When you're in a situation like this, on the bench and not getting a lot of playing time, you have to stay alert and try to get back in the lineup," he said.
Cintron started much of last season at shortstop but lost his starting role with the acquisition of Royce Clayton.
"I'm a young guy," said Cintron, who played just one game at third in 2004. "I would like to play every day. I'm the kind of guy who has to be in the game to stay successful. When I'm out there I'm not just playing for the Diamondbacks, I'm playing for the other 29 teams. You never know who's watching. I haven't been through this in my career since like Little League."
The Padres' defense nearly sent the game into extra innings with a brilliant ninth inning. After Clayton led off with a single, Dave Roberts robbed Luis Gonzalez of an extra-base hit with a diving catch in center field.
Chad Tracy then hit a high popup behind second base. Second baseman Mark Loretta, with his back to the bag, dropped the ball but turned and threw to pitcher Akinori Otsuka (0-1) to force Clayton at second as Tracy reached first.
Shawn Green singled to right and Cintron lined a hit in front of defensive replacement Xavier Nady in left to score Tracy with the winning run.
Mike Koplove (2-1) pitched a hitless ninth to earn the win for Arizona.
San Diego starter Jake Peavy held the Diamondbacks scoreless over the first six innings. Peavy faced only two hitters over the minimum and did not allowed an Arizona runner to reach second until Green's two-out double in the seventh. Cintron hit Peavy's next pitch off the base of the right-field wall to tie it at 1.
Peavy struck out pinch-hitter Tony Clark, his eighth, to escape the jam. Peavy allowed four hits and walked one in seven innings.
"He pitched his heart out," San Diego manager Bruce Bochy said. "We're just not hitting. They shut us down. We only hit a couple of balls hard. He deserved better."
Brandon Webb was nearly as sharp for Arizona, scattering five hits over eight innings with five strikeouts and a walk. Webb, the NL leader in walks a year ago, allowed just five balls to reach the outfield, four of them Padres hits.
"We could have played everybody in the infield and gotten away with it," Arizona manager Bob Melvin said. "He can throw the ball over the plate and that's the difference between last year and this year. He's comfortable throwing the ball over the plate."
San Diego scratched out a run when Phil Nevin led off with a double, moved to third on a ground out and scored on Carlos Hernandez's roller to second.
"The boys are going to talk about not getting me runs," Peavy said. "But they got me one against a very tough opponent. On nights like tonight it's my job to hold that lead so obviously it's very disappointing. I've got to let it go. We're going to match up again Friday night in San Diego."
The Padres threatened again in the sixth. Brian Giles hit a two-out single, stole second and went to third when Webb's throw home bounced in front of the plate and high off catcher Chris Snyder. But Webb fought back from a 3-0 count to strike out Nevin and end the inning.
"You want to go against the best guy they have," Webb said. "To get the matchup and pitch as well as I did, it's pretty sweet."
Webb got some defensive help from Tracy, who stopped a two-out rally in the third. With Loretta on second, Tracy stopped Giles' hard grounder in the hole and slid into first ahead of the runner for the final out of the inning.
Nevin's double extended his hitting streak to eight games. ... Webb recorded 18 of his 24 outs on the ground. All but 11 of the 82 outs Webb has recorded this year have been on ground balls. ... Peavy entered the game 1-4 with an 11.20 ERA at Bank One Ballpark. ... Arizona 3B Troy Glaus was out of the starting lineup for the first time this season, one night after hitting his NL-leading sixth homer, leaving Green as the only player to start every game for the Diamondbacks.