If the Cubs are holding a trump card in their hand, it's their collection of starting pitchers. It's almost always bad news when one of Dusty Baker's front four asks his free-swinging teammates to win slugging contests.

Matt Clement did just that Tuesday night. This is no way to win a division title, even in such a friendly neighborhood as the National League Central, circa 2003.

Clement, who had worked at least five innings in 22 of his last 23 starts, got pounded for eight runs in four innings. He twice surrendered leads to the Houston Astros, who survived an unlikely rally against closer Billy Wagner to win 12-8 in the opener of a three-game series at Minute Maid Park.

Umpire Laz Diaz's call on an apparent error by second baseman Jeff Kent in the ninth inning deprived Sammy Sosa of a chance to extend the game. Diaz ruled Kent had controlled a throw from third baseman Geoff Blum, which appeared simply to pop out of his glove. It might not have mattered, however, as Sosa flied to right to end his night 0-for-5.

Manager Dusty Baker disagreed with Diaz's call, which kept the Cubs from having the bases loaded with no outs in the ninth.

"He said he was going to exchange the ball," Baker said. "But his throwing hand was never in position to do it. It looked like he flipped it out of his glove."

Kent had a three-run homer and drove in six runs to lead a 15-hit attack for the first-place Astros, who increased their lead to one full game in the three-team Central race. St. Louis, which beat Pittsburgh, moved past the Cubs into second place.

The Cubs have lost three in a row, falling back to four games above .500 and 1½ games behind Houston. This latest slide started on Saturday, when Kerry Wood got knocked around in a 10-5 loss to Los Angeles.

Baker will look to his horses to end the trend. Mark Prior faces Jared Fernandez on Wednesday night and Wood is scheduled to work Thursday night, if his back is deemed sound.

That game will be the last of the season between these two Central rivals. The Cubs lead the series 8-6.

If nothing else, Moises Alou climbed into Jimy Williams' head on Tuesday. The Astros' manager couldn't win when it came to Alou.

Acknowledging the series' importance, Williams intentionally walked Alou with two outs and Alex Gonzalez on second base in the first inning. Aramis Ramirez responded by crushing a 2-2 meatball from fading rookie Jeriome Robertson (1-3 with an 8.53 ERA in his last five starts) off the brick wall that rises above the left-field bleachers.

Clement couldn't make that 3-0 lead hold up for even an inning, however. Houston scored four in the bottom of the first, with doubles by Jeff Bagwell and Geoff Blum the biggest blows.

Alou gave the lead back to Clement in the third. Williams pitched to him with Kenny Lofton on third and two outs. Alou drove a 1-1 pitch into the box seats atop the left-field wall for his 19th homer.

Clement never got it rolling, however. Gregg Zaun tied the score, 5-5, with a third-inning single.

"I really didn't want to [take Clement out] early," Baker said. "You start out like that on a road trip and you're in trouble. I didn't want to get through my bullpen the first night. I didn't want my bullpen upside down."

With no one even warming up, Clement walked Lance Berkman and Bagwell in the fourth. Kent, who had driven in a first-inning run with a single, followed with a mammoth homer down the left-field line.

He wasn't finished. Kent split the gap in left-center with a two-run double off reliever Dave Veres in the sixth inning, pushing Houston's lead to 10-5. It would grow to 12-5 before Kyle Farnsworth could end that nine-batter inning.