I'm not the first to point this out, but let's note that Don Mattingly is officially a curse wherever the hell he goes, especially when it comes to a team's post-season fortunes. Nuts? Let's take a brief chronological tour.
1982-1994: Mattingly is a productive member of the Yankees. Not coincidentally, they fail to make the playoffs a single time, though the '94 strike probably didn't help.
1995: The Yankees make the playoffs for the first time, despite the presence of Mattingly, and do so thanks to the improbable events of Scott Kamineicki throwing a 1-run complete game on the next-to-last day of the year, one day after Pat Kelly hits the game winning home run to put them in the wildcard lead. The baseball gods, too busy fucking with the fortunes of the Angels, right the ship by torturing the Yanks in a 5-game loss to the M's.
1996: Ridden out of town on a rail, Mattingly contemplates going to Japan, and instead retires to Indiana. The Yanks win the World Series for the first time in 18 years.
1997: Donnie Baseball returns to have his number retired. Shoulda stayed away. Yanks drop to the Indians in the Wild Card round, in the process making Jaret Wright a postseason hero.
1998-2003: Mattingly's exile continues. During this six-year span, the Yankees make the World Series 5 times, winning three of them, and coming ooooooh so close in 2001.
2004-2007: The Yankees bring in Mattingly as their hitting coach, for no apparent reason. Despite having an enormous payroll and the best player in baseball, the best they can muster is a wild card round win against a crappy Twins squad, after which they embark on the biggest collapse in baseball history, and fail to get out of the first round 3 straight years.
While I can't say that Hank and Hal have thought this out that carefully, you have to think this is part of the reason Girardi got tabbed for the managerial post. But now the Dodgers are thinking of bringing him in with Torre. Word to the wise Mr. McCourt: stay away. Stay far, far away.