For the third time in what Thursday night became a seven-game losing streak, rookie shortstop Troy Tulowitzki put the Rockies ahead with a home run in the top of a deciding inning and Fuentes blew it.
This time, Carlos Lee's grand slam in the bottom of the 11th gave the Astros an 8-5 victory before a Minute Maid Park sellout crowd of 42,537, which saw Craig Biggio tie a career high with five hits and become the 27th member of the 3,000 hit club.
"I'm fine," Fuentes said. "I'm just in a bad stretch right now. Every time I go out, I expect to get the job done. It just hasn't happened."
The same bizarre scenarios keep happening to the Rockies.
Tulowitzki's home run was his fifth in the last eight games. The last three -- in the 10th inning at Toronto on Friday night, in the ninth against the Cubs on Monday night and Tuesday night's off Brian Moehler (1-2) should have been game-winners.
But soft hits, the occasional bad pitch and shoddy defense at the wrong time have done in Fuentes (0-3), who suffered his fifth blown save in 25 chances.
Fuentes fanned Luke Scott and worked Chris Burke into a fly ball. But Biggio, who hit No. 3,000 on an RBI single off Rockies starter Aaron Cook in the seventh, beat out a slow roller, and the inning turned strange.
Hunter Pence tapped a roller past Fuentes. Tulowitzki and second baseman Kazuo Matsui each appeared to be close enough to grab it, but neither did. Matsui said he didn't see it roll beneath Fuentes' glove. The previous two losses featured errors.
Fuentes hit Lance Berkman, then Lee golfed a changeup over the left-field wall.
Fuentes wasn't the only reliever to suffer. LaTroy Hawkins, who had given up one run in his previous 14 appearances, was handed a 4-1 lead in the eighth and lost it on a Berkman solo shot and Mike Lamb's two-run shot.
"You look at the entire game," Rockies manager Clint Hurdle said. "We're just missing in some areas that we can put things away or close things out. We're just not getting it done."
Several strong performances went unrewarded.
Cook, who had lost his last three starts and struggled mightily in two of them, went seven innings and held the Astros to one run on seven hits -- three by Biggio.
Chris Iannetta went 2-for-3 with a home run off Astros starter Roy Oswalt and an RBI single and Ryan Spilborghs knocked a pinch-hit, two-run homer off Chad Qualls in the seventh.
"Anytime you lose seven in a row, it's frustrating -- especially the way we've lost them at times," Iannetta said. "Hopefully we can play a little bit better, and just blow somebody out."
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.