Michael Bourn and Pence walked with no outs in the eighth to set up the decisive rally. Both runners moved up on Cla Meredith's wild pitch before Carlos Lee tied it with an RBI single. Tejada followed with a grounder to the left of the mound and Pence took off.
"I was saying no, no, no," manager Cecil Cooper said, "then I was saying yes, yes. That's just Hunter's aggressiveness. Sometimes he's a little too aggressive but I wouldn't change a thing about him. That's how we want him to play."
Pence had no doubt about the play.
"Basically, they said to see it through unless it was a chopper," Pence said. "I read it as a chopper so I came as fast as I could."
Meredith didn't field the ball cleanly enough to have a chance on Pence.
"I tried to barehand it," he said. "My glove was right there. I tried to give it a go. I thought it was my only shot. I knew I had to be quick. Unfortunately I couldn't get the transfer."
Chase Headley hit a two-out, two-run double off LaTroy Hawkins (1-0) in the top half to give San Diego the lead. But Hawkins got Nick Hundley to foul out to first with the bases loaded to end the inning.
"It was a great sign we rallied, got some big hits," Padres manager Bud Black said. "I hope this is a sign of things to come, getting three runs in the eighth, getting some good swings and at-bats.
"In close games, to lead off the inning with a walk, that's one of the things the younger pitchers are going to have to learn to control. Then we have the wild pitch. Those things late in the game will haunt you."
Luke Gregerson (0-3) allowed a run in the seventh and was charged with both runs in the eighth as the Padres lost for the third time in four games.
David Eckstein doubled in a run in the sixth and had an RBI single in the eighth for San Diego.
Brian Moehler had a strong start for the Astros, allowing one run and five hits in seven innings. He was making just his second start after spraining his right knee, and had an unsightly 14.00 ERA in three starts coming in.
Kevin Correia lasted six innings for San Diego, allowing two runs and four hits.
The Astros moved Russ Ortiz to the bullpen and put rookie Felipe Paulino in the rotation. Paulino had three quality starts after being called up. "It's their decision to make, but I'm not happy about it," Ortiz said. ... Houston slugger Lance Berkman missed his second straight start with a sprained left wrist. Berkman tried one swing in the batting cage and pronounced himself unable to go. He's day to day. ... Astros SS Tejada and Padres 1B Adrian Gonzalez lead the league in innings played. Both have played every inning this year.