Oswalt came off the disabled list and struck out five in the Houston Astros' 5-4 win over the Reds on Monday night.
Oswalt (8-8) won his fifth straight start against Cincinnati and improved to 20-1 in 25 career outings against them, despite giving up a grand slam to Adam Dunn. The Houston ace threw 74 pitches in his first start since aggravating a left hip injury on July 11. He went on the DL on July 19 and was activated just before Monday's game.
He was hoping to throw 80-85 pitches, but felt fatigued by the end of the fifth.
"There wasn't a whole lot of sense to go out there and maybe face one batter and come out," Oswalt said. "We decided the fifth inning was enough."
Oswalt left the July 11 start in Washington after one inning. He had gone at least six innings in 15 of 18 starts before that, but Houston manager Cecil Cooper isn't worried about Oswalt's conditioning right now.
"He's back. That brings a smile to my face," Cooper said. "He's back, he's feeling good and we just thought five was good enough."
Geoff Blum hit his third homer in two days and Jose Valverde pitched a perfect ninth to earn his 27th save. The Astros' bullpen allowed one hit in four scoreless innings as Houston beat Cincinnati for the seventh straight time.
Johnny Cueto (7-10) gave up five runs and eight hits for the Reds, who've lost four in a row and six of their last eight.
The Astros took a 2-0 lead before Cueto recorded his first out.
Blum lined out to center and Berkman tagged up from third to make it 3-0. Cueto threw 33 pitches in the first inning.
The Reds had a scoring chance in the second when Brandon Phillips doubled and Dunn singled to put runners at first and third with no outs. Oswalt struck out the next three batters.
"We knew with Oswalt coming off the disabled list, he would be on a limited pitch count," Cincinnati manager Dusty Baker said. "We got two runners on in the second, he struck out the side and I got a headache."
Oswalt was surprised how well he located his pitches after the long layoff. Of his 74 pitches, 54 were strikes.
"I thought I'd be kind of all over the strike zone," he said. "I had good command of the curveball and the fastball."
Dunn hammered the first pitch off the center-field wall, above the yellow line for a home run. The 426-foot shot was Dunn's ninth career grand slam and his second in less than a week. He also hit one on July 23 against San Diego.
Berkman doubled in the Houston third before Blum homered to right center, his ninth of the season and third in two games. Blum hit a pair in the Astros' 11-6 win over Milwaukee at Miller Park on Sunday.
Last week, Blum watched film of at-bats from earlier in his career. He made an adjustment, then went 3-for-8 in the Milwaukee series over the weekend before his three-RBI night Monday.
"I saw some things I was doing with my hands that are a little different than I'm doing now," he said. "Kind of went back and tried it a little bit and it's obviously working out."
Berkman made a diving catch on Javier Valentin's liner for the final out.
"It's been a long time since I saw a pitcher leave after the fifth inning with a one-run lead and still win the game," Baker said.
Griffey has an 11-game hitting streak. ... The Astros have won 12 of the last 15 meetings with the Reds. ... The Astros activated Oswalt from the disabled list before the game and optioned RHP Runelvys Hernandez to Triple-A Round Rock. Hernandez started four games and went 0-3 with an 8.38 ERA in 19 1/3 innings. ... Astros CF Michael Bourn sat out with a sprained right ankle. Cooper said Bourn could return to the lineup on Tuesday, but "that's not a for-sure thing."