Mark Prior pitched five shutout innings in his third start since coming off the disabled list and Todd Walker homered twice, ending Roger Clemens's unbeaten start with a 7-2 win over the Astros in Houston last night.

A highly anticipated pitching duel between one of the game's most enduring stars and one of its newest was surprisingly lopsided in favor of the Cubs' 23-year-old all-star.

"Going against someone that's going into the Hall of Fame . . . it was just nice to beat him," Prior said. "It's pretty special because he doesn't give up many runs."

Prior (1-1) allowed five hits and struck out eight, denying his childhood idol a chance to become the first pitcher in the big leagues with 10 wins. Clemens also could have become the first Astro to start the season 10-0 since Juan Agosto in 1988.

Thome Hits Home Run No. 400

The Phillies' Jim Thome became the 37th player to hit 400 homers, connecting for a two-run shot in the first inning against Cincinnati in Philadelphia.

The crowd erupted as Thome hit his shot to left-center field. Thome pumped his right fist as he rounded first base and pointed to the crowd. He was mobbed by teammates when he reached home plate as the Phillie Phanatic deliriously danced on the dugout with a "400" sign.

The fans gave Thome a standing ovation and he emerged from the dugout for a curtain call.

Camera flashes popped all over the park on every pitch as he dug in against the Reds' Jose Acevedo. Fans gasped on several foul balls, thinking each swing would be the one.

The game was delayed three times by rain and ended too late for this edition.

Mark Prior (1-1) earns first win of season for Cubs, sending Astros' Roger Clemens (9-1) to his first loss. Prior tossed 5 shutout innings with 8 strikeouts; Clemens allowed 5 runs on 10 hits.