Opponent: Houston Astros (53-58).

Site: Minute Maid Park, Houston.

Times: 8:05 p.m. today, Wednesday and Thursday.

TV, radio: All games on FSN Pittsburgh, KDKA-AM (1020) and Pirates Radio Network.

Starting matchups: LHP Paul Maholm (4-9, 4.83) vs. RHP Brandon Backe (2-1, 4.38), RHP Shawn Chacon (1-0, 1.80) vs. RHP Roy Oswalt (8-7, 3.34) and LHP Tom Gorzelanny (2-2, 4.41) vs. RHP Roger Clemens (3-4, 2.32).

Season series: Houston leads, 4-2.

Three things you should know about the Astros: 1. The Astros, who swept three games from the Pirates April 21-23 in Houston, are last in the National League in team batting average and slugging percentage. 2. Second baseman Craig Biggio, 40, Saturday reached the 2,900-career hit plateau in his Hall of Fame candidacy. He's the 34th player to get at least 2,900 hits and the active leader in career hits. 3. The Astros Sunday finished a six-game trip to San Diego and Arizona on which they went 4-2. That followed a 2-4 homestand. "Until the people in uniform who take the field every day do something about it, you'd have to consider us a mediocre team at best," catcher Brad Ausmus told the Houston Chronicle.

The Pirates' key to success: Stay close until Houston closer Brad Lidge pitches. In his past 15 appearances, the right-hander has yielded 13 hits, including three home runs, and 10 runs in 12 2/3 innings.

The intangible: The Astros have scored no runs for Clemens in four of his nine starts this season.

On deck: Pirates begin a three-game series against St. Louis Friday night at PNC Park.