Simply put: You cannot argue with this hire. If you do, you're really stretching things. Mazzone has a proven track record and I don't think I've ever heard a bad word about him. I think it's about as exciting as hiring a new pitching coach can be.
A lot of his success can be attributed to the fact that he was coaching Greg Maddux, John Smoltz and Tom Glavine, yes. But then there are the years he got out of a lot of other, less-talented pitchers. Jaret Wright got $21 million from the Yankees at least in part thanks to Leo Mazzone's help. And just going through the starters doesn't even consider the work he's done with a lot - a LOT - of retread Atlanta relievers. Chris Hammond and Darren Holmes in 2002, anyone? What sense did those guys make?
Recommended Read: 'The Mazzone Effect' @ BaseballAnalysts.com