ST. LOUIS -- There appears to be no such thing as a safe lead for the Milwaukee Brewers, who continue to struggle away from the comforts of Miller Park.

A day after they squandered a six-run lead in Game 1 of a doubleheader, the Brewers built a five-run lead on Sunday, only to see this one slip away as well. Reliever Carlos Villanueva walked in the go-ahead run in the eighth inning of a 9-5 Brewers loss at Busch Stadium that left the team clinging to only the smallest of margins in the National League Central.

Losing pitcher Derrick Turnbow (2-4) was charged with four of the Cardinals' five runs in the decisive eighth, and the Brewers finished the trip to Cincinnati and St. Louis with a 2-6 record. The Cubs beat the Reds on Sunday and pulled to within a half-game of the fast-fading Brewers.

"If anybody is frustrated, we're frustrated with ourselves," Villanueva said, "because we know we're better than this. It's not because the Cubs are winning. They're doing what they're supposed to do, and it's up to us to do what we're supposed to do, and that's win. We know we have the guys here to do it."

The Brewers are idle on Monday, so whether they hold sole possession of first place depends on the Cubs-Phillies game Monday night. Manager Ned Yost closed the clubhouse doors briefly after Sunday's loss and, as he told it, simply told players to keep their heads up.

The good news is that they are headed back to Miller Park, where the Brewers are 36-17 this season. Sunday's loss left them with a 21-32 road record that no one can quite figure out.

"That's the million dollar question," Turnbow said. "Who knows, but we need to figure it out some how, some way, and very quickly."

For the second straight day, things started in promising fashion for the visitors. The Brewers built a 5-0 lead on St. Louis right-hander Kip Wells, whom they had already defeated twice this season, and who surrendered 11 hits in his five innings on Sunday. Catcher Johnny Estrada hit a two-run single in a three-run third inning, and starting pitcher Yovani Gallardo laced a two-out, two-run single in the fifth after Wells intentionally walked Rickie Weeks.

Gallardo cruised through four hitless innings, but suddenly began to struggle in the bottom of the fifth, allowing four runs and letting the Cardinals back in the game. He threw 33 pitches in the frame, including nine to Cards shortstop David Eckstein, who swung through Strike 1 but then fouled off seven consecutive pitches before doubling in the third run of the inning.

Eckstein took third on Estrada's passed ball and scored on a Ryan Ludwick groundout.

"I tend to rush a little bit sometimes," Gallardo said. "That happened in the fifth inning. It's just one of those innings where they tried to get something started and I have to stop it. I gave up a leadoff double and then walked a guy, and after that I wasn't able to step off, relax and just take my time a little bit more."

The big inning pushed Gallardo's pitch count to 100 (67 of those were strikes) and prompted an early call to the bullpen. Brian Shouse worked a scoreless sixth inning and Scott Linebrink pitched out of a bases-loaded jam in the seventh to get a 5-4 lead to Turnbow, the team's eighth-inning specialist.

All four Cardinals hits off Turnbow were singles. With two on and one out, Scott Rolen tied the game and notched his 1,000th career RBI with a single to center field. When Eckstein loaded the bases with another hit, Yost elected to call for Villanueva.

Ludwick battled to a full count, taking what Villanueva and Estrada described as Villanueva's best slider of the day before drawing the go-ahead walk.

"You have the bases loaded right there, you're trying to get the guy to 'fish,' and how he laid off the 2-2 pitch to make it 3-2, that's a tough pitch for a young kid to lay off," Yost said.

Villanueva then got ahead of Albert Pujols, 0-and-2, but Pujols turned on an inside pitch and cleared the bases with a three-run double that put the game out of reach.

"That's a pretty good-hitting club over there," Yost said. "I've never felt comfortable, especially in this ballpark, with a lead. Like the first night [Friday], we had a huge lead and I never felt comfortable. Those guys can really swing the bat."

Whether the Brewers will still remain comfortably in first place is up to the Cubs on Monday.

"It wouldn't be fun if we always had the lead," Villanueva said. "We have to work for it. In the end, if we prevail, it's going to be so much sweeter."