"It got away quick," Villanueva said.
The rally came just in time for Houston starter Roy Oswalt (3-3), who was not exceptionally sharp over six innings while allowing four Brewers runs on six hits, including Ryan Braun's two-run first-inning home run and Mike Cameron's solo homer leading off the fifth, Cameron's first as a Brewer.
Astros closer Jose Valverde hit Prince Fielder with a pitch leading off the ninth inning, but never let the tying run come to bat for his sixth save.
An emotional Villanueva took the mound for Milwaukee with a chance to lift his sagging teammates, who were still stunned by the unexpected severity of Gallardo's knee injury. The right-hander has a torn ligament in his right knee and might not be able to contribute to the Brewers' drive to end a 25-year postseason drought.
Villanueva might have gotten the news first, in a text message Friday morning from Gallardo after the pitcher was examined by the team doctor in Milwaukee.
"I think I have a torn ACL," Gallardo wrote.
"I was like, 'What?'" Villanueva said. "I had to call and ask if he was serious. ... It's definitely a sad thing for him, for us, for our team, and we have to step it up. The rest of us have to step up because he was a big part of our plan for the season. Him going down right now doesn't really help our chances."
For four innings, Villanueva triumphed, retiring the first 11 hitters he faced and 12 of the first 13.
Then, in what seemed like an instant, everything went wrong, just like it did for Gallardo. Villanueva surrendered hits to eight of the final 10 hitters he faced, including back-to-back-to-back home runs to the final three.
"He was at 60, 65 pitches. Fatigue is not an issue," Brewers manager Ned Yost said. "He just couldn't get the ball down. In this park, man, that is a death sentence."
Lee doubled leading off the fifth inning before Hunter Pence, who entered the game with one home run this season, connected on the first of his two in the game.
Kaz Matsui led off the Astros' sixth inning with a soft single fielded by Villanueva, and Tejada connected on a curveball to tie the game at 4. Berkman followed and poked a high fastball to the Crawford Boxes for a short-porch home run, and Lee worked an eight-pitch at-bat that ended with another homer to left.
"It is kind of striking," Yost said. "The first four innings you give up one hit, and the next [two innings], you give up eight. It just kind of snowballed on him."
The reason, Villanueva said, was simple.
"I kept the ball 'up' a couple of times, and every time I did, they didn't miss it," Villanueva said. "Even after the game was tied, I said, 'Don't let it get out of hand.' The bad thing was they weren't singles. You can't defend the home run."
None of Houston's three homers in the sixth inning were particularly towering shots. Lee's was the longest at 378 feet, Tejada's traveled 365 feet and Berkman's just 347 feet.
At cozy Minute Maid Park, they were all deep enough.
"I hate that," Villanueva said. "[But] you can't change that. All you can do is keep the ball down, make them hit it on the ground."
Said Yost: "Still, they're home runs. You play the park. It doesn't matter if they're [in the] Crawford Boxes or not. They're home runs. That's the way the stadium plays, and you have to keep the ball down so that doesn't happen."
He added: "All three pitches, none of them were any good."
The Brewers had opportunities. They left the bases loaded in the second and fifth innings against Oswalt, and in the seventh inning against Geoff Geary.
Cameron's homer leading off the fifth inning made it 3-0, and five batters later, J.J. Hardy reached on an infield RBI single that left the bases loaded with one out. Oswalt struck out Villanueva looking and retired Jason Kendall on a groundout.
"A couple of times, we got him on the ropes and he got out of a couple of jams," Cameron said of Oswalt. "That set it up for their big boys. We weren't expecting them to go deep three times [in a row]. That's what this ballpark is conducive to."