Clemens lasted just three innings -- his shortest outing in more than a year -- as the Astros lost to the Milwaukee Brewers 7-4.
"What I took out there is not going to get it done," Clemens said after giving up a season high-tying five runs. "I need to obviously be sharper, a lot sharper than what I took out there. Just too many walks."
Clemens walked five, also matching a season high, and gave up five hits in losing his third straight decision.
His major league-leading ERA jumped from 1.57 to 1.78.
It is Clemens' longest single-season losing streak in five years.
Despite the loss, Houston remained a half-game ahead of the Florida Marlins for the wild card with Florida's 12-5 defeat Friday at Philadelphia.
"It just goes to show you that anybody can have an off night," Astros first baseman Lance Berkman said. "He is just a great performer, and you expect him to throw well. At the same time, he's a human being, too."
Doug Davis gave up three runs and six hits in five innings to earn his 10th win. He struck out six.
Davis (10-10) last won on June 22, and had 10 no-decisions since.
Brewers manager Ned Yost thought that getting Davis his long-awaited 10th victory against the Astros and Clemens "looked like an impossible task."
"You really can't count on scoring five runs off of Roger Clemens, but tonight, luckily, we did," Yost said. "Any time you can beat him, you've done something."
Derrick Turnbow pitched the ninth for his 30th save in 33 chances, including his ninth straight.
The outing was Clemens' shortest since Aug. 18, 2004, when he pitched three innings at Philadelphia, giving up four runs and five hits on 47 pitches in a no-decision.
Clemens, who entered the game with a 0.52 ERA on the road, struggled from the start.
Hardy hit a first-inning homer to left, and after Jason Lane's homer tied it, Miller hit a two-run drive in the second for the Brewers.
Clemens had given up just eight home runs all season.
Clemens sparked a rally in the third, but also may have jeopardized his start in the process.
He led off the inning with an opposite-field double over the head of Geoff Jenkins. Astros manager Phil Garner and head trainer Dave Labossier went out to check on Clemens, who strained his left hamstring in his last start Saturday against St. Louis, but he stayed in the game.
Clemens scored on Berkman's bloop single.
Clemens said the hamstring felt fine, but Garner wasn't so sure.
"It was rare," Garner said of Clemens' struggles. "We have not seen that from him really all year. Tonight, he just never did get it. I think the leg did have something to do with it. He said it was OK."
Clemens struggled in the third. He walked Lyle Overbay and Carlos Lee with one out and Bill Hall with two outs to load the bases. Weeks then lined a single past shortstop Adam Everett to drive in two. After an intentional walk to Miller, Davis grounded out to end the threat.
Milwaukee added single runs in the sixth on an RBI single by Lee and seventh on an RBI single by Hardy.
The loss spoiled Jeff Bagwell's return from the disabled list for the Astros. The 37-year-old Bagwell, who had missed 115 games after having right shoulder surgery June 7, was activated from the 15-day disabled list before the game. He pinch hit for Clemens with a runner on second base in the fourth and struck out looking.
Garner said Bagwell will serve only as a pinch hitter the rest of the season, providing a small boost to an offense that ranked as second-worst in the National League in batting average (.255) and hits (1,197) and 14th in RBI (556) entering play.
- Clemens lost three straight starts from May 23 to June 9, 2000, as a member of the New York Yankees. He also lost his last two decisions of the 2001 season and first start of 2002 with New York.
- Clemens has not lost four straight decisions since May 28 to July 6, 1996, as a member of the Boston Red Sox.
- Lee extended his hitting streak to 11 games with a first-inning infield single.