Analyzing the components of Tuesday's trade that sent Mike Williams to Houston:

To the Astros:

Mike Williams, RHP
Mike Williams(Allsport)	What's to gain: One of the National League's best closers this season on one of the league's worst teams. Among pitchers with 20 saves, only Armando Benitez has fewer blown opportunities. If his nasty-breaking slider doesn't strike out a hitter, he'll most likely ground out. The former washed-out starter can work three consecutive days without concern.
	What's to lose: Williams' success hinges on the slider. If it's not working, he's in trouble with an average fastball that lacks movement. His groundout-to-flyout ratio is lower than usual this year despite a great new park for grounders in Pittsburgh.
	What's his role: Work setup duty for the equally effective Billy Wagner before seeking a closing job again as a free agent this winter.

To the Rockies:

Tony McKnight, RHP
Tony McKnight(Allsport)	What's to gain: A future mid-rotation starter who satisfies GM Dave Littlefield's need for young pitching. The 1995 first-round pick has shined in the minors since 1999, including a 9-5 record at Triple-A this season. He hits his spots with a strong fastball and curve plus a change. He pitched effectively in three Houston starts this year and six last season.
	What's to lose: McKnight is a late bloomer after elbow and shoulder woes stalled him for three years. He thus fell behind Houston phenoms Roy Oswalt and Tim Redding, who are around the same age.
	What's his role: McKnight will likely get his shot immediately in Pittsburgh's rotation this year.