HOUSTON -- Andy Pettitte thinks he is pitching better than ever before.
Pettitte (13-9) improved to 10-2 in 14 starts since June 20. The left-hander lowered his ERA to 2.50, tied with Washington's John Patterson for third best in the National League.
"I feel I'm a better pitcher right now than ever before," Pettitte said. "I'm using my changeup more and that's helping and I'm just getting smarter and not worrying much about velocity."
Pettitte had elbow surgery that ended his 2004 season last Aug. 24 and caused him to get off to a 3-7 start this year. But he now thinks the ailing elbow might have contributed to his improved performance.
"There's no doubt," Pettitte said. "The elbow hasn't allowed me to over-pitch. It's helped me be more consistent. If I was healthy, I'd probably get stupid and rare back and just try to throw hard sometimes."
Brandon Claussen matched Pettitte for four innings before the Astros broke open the game with a four-run fifth.
"We put together some big hits tonight," manager Phil Garner said. "Lost in all that was the fact Andy pitched seven shutout innings. He has just been phenomenal for us.
"He has pitched well for most of the season. It seems like he's been pretty good for a couple of months."
Astros catcher Brad Ausmus drove in four runs and helped the fifth-inning outburst. He also praised Pettitte's strong showing.
"He did a great job," Ausmus said. "I don't think he was feeling 100 percent, but he's got the mental wherewithal to overcome any kind of tenderness or soreness."
The Reds couldn't tell if Pettitte was hurting.
"He's one of the best pitchers in the game," Jason LaRue said. "Every time he's out there, he doesn't make too many mistakes and tonight he didn't make too many mistakes. Sometimes you just have to tip your cap when you go up against some pitchers."
Adam Dunn agreed.
"He was back to his old self," Dunn said. "The first time we faced him, he didn't have his velocity back to where it was tonight. When he is spotting his pitches like he was tonight, he's one of the best.
"He has his confidence back and it showed tonight."
Jason Lane hit a two-run homer for the Astros, who remained a half-game behind Philadelphia in the NL wild-card race.
Claussen (9-9) lost for the first time since July 23 against Milwaukee. He had gone 5-0 in six starts since, the longest win streak by a Reds pitcher this season.
Claussen allowed only two hits in the first four innings before the Astros bunched five consecutive hits to score four runs in the fifth.
"I was aggressive in the strike zone," Claussen said. "They may have changed their approach in the fifth. They were jumping on the first pitch.
"The home run ball to Jason Lane was four inches off of the ground. It was a good pitch but he was able to put the bat on the ball, get it elevated and get it out. I might have been just a hair up in that inning but I was still aggressive in the strike zone."
Lance Berkman led off with a double and Lane hit his 20th home run for a 2-0 lead. Chris Burke and Adam Everett each singled and Ausmus drove them home with a double to right-center.
Ausmus tried to stretch the hit to a triple and was called out on a close play at third, which Garner argued.
Claussen lasted 5 2/3 innings and allowed four runs on eight hits. He walked none and struck out three.
Back-to-back RBI singles by Willy Taveras and Craig Biggio off Jason Standridge made it 6-0 in the seventh.
Ausmus had a two-run single and Jose Vizcaino hit a two-run homer in the eighth off Randy Keisler.