Houston ? Mark Prior, Todd Walker and the Chicago Cubs finally made Roger Clemens look his age.

Prior pitched five shutout innings in his third start since coming off the disabled list, and Walker homered twice, ending Clemens’ unbeaten streak at 13 games with a 7-2 win over the Houston Astros on Monday 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 only five hits and struck out eight, denying his childhood idol a chance to become the first pitcher in the big leagues with 10 wins. The 41-year-old Clemens also could have become the first Astro to start the season 10-0 since Juan Agosto in 1988.

Clemens (9-1) hadn’t lost since Sept. 6, 2003 against Boston, when he was with the New York Yankees.

Walker went 4-for-5 with homers in the sixth and ninth and a triple in the third. He also scored four runs. The Cubs’ second baseman is now 14-for-29 in his last six games after going 0-for-13 in his previous four.

Aramis Ramirez and Moises Alou also homered, handing the Astros their third loss in four games.

Houston, the NL’s top-hitting team, has failed to score more than five runs in a game since a 7-1 win over St. Louis on May 30. That’s a stretch of 13 games.

Houston pitcher Roger Clemens reacts after giving up a triple to Chicago Cubs infielder Todd Walker. The Cubs beat the Astros, 7-2, Monday in Houston.

The Astros’ problems were compounded by the loss of shortstop Adam Everett, who left the game in the first inning after straining his left hamstring while running out an infield single.

“Offensively, we stink right now,” Houston catcher Brad Ausmus said. “We do need to expect more of our offense right now.”

The Cubs showed no weariness following Sunday’s 15-inning thriller against the Anaheim Angels, a 6-5 victory that took 5 hours, 8 minutes to complete.

Prior struck out four of the first five batters he faced and didn’t allow a runner past first base until Jose Vizcaino’s double in the fourth. He retired the side in order in the fifth.

After Lance Berkman doubled deep to center in the sixth, Prior departed to a smattering of applause from a small contingent of rowdy Cubs fans. Jimmy Anderson replaced him and went the final four innings for his first save.

“That was a great performance by Mark Prior,” Cubs manager Dusty Baker said. “He had everything but endurance and stamina. We’re gonna keep him on a pitch count until he can build up his stamina some.”