There's an opening. And there's a need. In Buster Olney's Insider-only blog post, he mentions the impending free agency of Tony La Russa. And then there are some managerial positions open. And what do you know? Houston is one of those places.
Olney:
The decks are cleared in Houston, and Drayton McLane is in perfect position to wrest La Russa away from a division rival, if he wants to -- and the timing might not be bad, considering that the Astros have so much money locked up in aging veterans that they don't have a lot of flexibility to make other moves. For less than what it would cost to sign Carl Pavano, the Astros could drum up tremendous interest in their team by adding La Russa and Duncan.
Olney also points out that Richard Justice wants Jim Fregosi, and of course, Justice doesn't mention Tony La Russa as a possibility - because Justice is having a hard time thinking outside the box.
Know this: the Astros will be immediately relevant on a national level (until the Yankees fart) if they get La Russa and Duncan away from St. Louis. Want to take a rivalry to the next level? Take their guys. And if La Russa and Duncan are pissed at the Cardinals, then this would be the logical equivalent of pouring kerosene on a wooden bridge.