"We just thought if we had a chance to move forward, we'd take advantage of it," Astros general manager Ed Wade said. "They've both epitomized the professionalism that we pride ourselves on and are very talented guys. Their presence on the club speaks for itself."

Moehler, 36, is 9-5 with a 3.99 ERA in 25 games this year, including 20 starts. He made the team as a non-roster invitee and worked his way into the rotation, going 4-1 since the All-Star break.

"It's great," Moehler said. "I'm very excited. I think a lot of this organization. I could have tested the free agent market, but I think we've got a legitimate shot at winning here. I think the pieces are in place. We have to go out and do it, and that's the main reason I signed back here."

Erstad, 34, has proved to be invaluable this year, hitting .293 with three homers and 26 RBIs in 119 games. He has started 32 games in center field, nine in left, six in right and six at first base.

"It was tough at first," Erstad said. "I played every day for quite a few years, and the last two I was hurt for most of the time. It's that time in my career for a different role. The guys we have on the team make it a lot easier because you want to pull for them; you want to pick them up because they play hard. I'm here to do whatever I can to help."

ASTROS 3, CARDINALS 2: Lance Berkman slugged the first walk-off home run of his career, sending a Russ Springer pitch into the Crawford Boxes in the ninth inning. The Astros won their third game in a row to improve to 19-9 in August, their winningest month since they went 22-7 in July 2005. All of their runs the last three games have been via the long ball. Trailing 2-0 in the seventh, 2B David Newhan hit a two-run homer off Cardinals starter Kyle Lohse to tie the game and set the stage for Berkman's ninth-inning heroics.