Because, man. That would suck. Like it wasn't bad enough that the Astros had to run into C.C. Sabathia, Ben Sheets, Carlos Zambrano (and his stupid, tainted no-hitter).
However, I don't think Sabathia and Burnett will impact the Yankees like Everyone thinks they will. Burnett will - at best - replace Mussina. Sabathia will only affect 20% of the Yankees 2009 season.
That said. Peavy owns the Astros, but he didn't play Us that often. Two games in 2008 (1-0, with a 2.77 ERA). However, if the Cubs rotation becomes Peavy, Zambrano, Harden, Dempster and Lilly? That would suck. Especially if, in an ideal scenario (a 5-game set), we see Peavy-Oswalt, Zambrano-Wandy, Harden-Hampton, Dempster-Moehler, Lilly-Backe. Maybe - MAYBE - the Astros take two of those games. And only the second if Lance decides he's going to eat Zambrano's face during the game.
Let's see how the Astros fare against Roy's BFF:
Blum - .500 (4x8 - not kidding)
Tejada - .444 (4x9 - still not kidding)
Lance - .250 (8x32)
Lee - .190 (4x21)
Pence - .167 (1x6)
Matsui - .143 (3x21)
That's bad. So to face Peavy four or five times? If this happens, it's the Cubs' division to lose. But then again, don't worry - they've been doing that for 100 years. Ha ha ha ha ha ha ha ha....
But to reiterate: Peavy to the Cubs is the worst thing that can happen to the Astros this season.