CHICAGO (AP) -- Not many teams call on a left-handed reliever to face Jeff Bagwell. The Houston slugger showed why Thursday.

Bagwell hit a three-run double off Mark Guthrie to spoil Ismael Valdes' Cubs debut and lift the Astros to a 6-2 victory over Chicago.

The Cubs didn't have many choices in the fifth inning when Bagwell stepped to the plate with the bases loaded and two outs.

Right-hander Matt Karchner was optioned to the minors before the game to make room on the roster for Valdes and another righty, Brian Williams, told pitching coach Oscar Acosta that he wasn't available.

Cubs manager Don Baylor said it was too early in the game to use Kyle Farnsworth.

That left a lot of lefties. Guthrie got the call and Bagwell hit the first pitch he saw to the base of the left-field wall to drive in three runs and open a 4-1 lead.

"I thought he would hit the ball at somebody," Baylor said of Bagwell.

"I was just trying to throw a sinker away and I made a bad pitch," Guthrie said. "It wasn't the pitch. It was the execution of the pitch that was bad. It was a horrible pitch."

Bagwell, who entered the game batting .500 against left-handers and .293 against right-handers, said teams have occasionally thrown southpaws at him before.

"Not many, unless it's a closer," Bagwell said. "(Guthrie) has a good forkball and I've been known to swing at a few in the dirt. But I was fortunate to get a first pitch fastball to hit."

Richard Hidalgo hit a solo homer for the Astros, who are now 8-7 on the road and 3-9 at new Enron Field.

Sammy Sosa and Joe Girardi homered for the Cubs.

Scott Elarton (1-0) had shoulder surgery in October and started the season on the disabled list. He won in his third start of the year.

Elarton gave up one run on four hits and two walks in six innings.

"I was really relaxed today and I don't really know why," he said. "My first two starts I had a little doubt in my mind."

Billy Wagner relieved with the bases loaded and two outs in the eighth. He barely held Houston's 5-2 lead, retiring pinch-hitter Glenallen Hill on a fly ball to the warning track to end the inning.

Wagner finished for his fourth save in five chances.

"We were debating in the ninth how many of these homers today would be out at Enron Field," Astros manager Larry Dierker said. "I think this environment is the toughest pitching environment we've played in."

Valdes, acquired with Eric Young from the Los Angeles Dodgers in a December trade, had been sidelined since March 20 because of tendinitis in his right shoulder.

Baylor wanted to limit Valdes (0-1) to 75-80 pitches, but the right-hander threw 93 in 4 2/3 innings. Valdes gave up four runs on four hits and three walks.

Valdes left in the fifth with the score tied at 1. He was pulled after Elarton singled and Craig Biggio and Roger Cedeno singled to load the bases with two outs.

"I had great, quality pitches," Valdes said. "Overall, I think it was a great outing for me. It's good to not feel pain."

Hidalgo hit his eighth home run and second in two games in the second. Sosa tied it with his ninth home run leading off the bottom half.

Girardi homered in the seventh off Mike Maddux. Tim Bogar hit a sacrifice fly in the Astros eighth to make it 5-2 and Ken Caminiti had an RBI single in the ninth.

Game notes
Sosa entered the game just 1-for-10 against Elarton. He went 2-for-3. ... Karchner was sent to the minors for the second time this season. ... Cedeno, who is 10-for-11 in stolen bases, was picked off at first base in the first by Valdes.