I found this paragraph on this web article (It is about 2/3rds down the page). I think it is the best way to describe the Yankee situation.
"In 1996-2000, it wasn't just that they had great chemistry (which they did), they didn't have nearly as much offensive talent so they were forced to play true October baseball. The current Yankee lineup isn't built for the postseason. You just can't rely on three-run homers with the great pitching in the playoffs, while you can in much of the regular season (especially playing Tampa and Baltimore 38 times). With a great set of contact hitters and speed guys --Damon, Jeter, Abreu, Melky, Cano -- this team should be hit-and-running, stealing at every opportunity, taking extra bases, bunting, etc. However, with power hitters like Sheffield and A-Rod clogging up the end of the lineup (such as Game 4, when A-Rod hit eighth), they can't. There is actually TOO MUCH talent. Are you honestly going to bunt with runners on first and second and no one out with the 25-million-dollar man up? Of course not. But if former eighth-place-hitter Scott Brosius is up, it's a no-brainer. So it's not just their lack of chemistry but the fact that playoff teams thrive off role players. Even if you take a loaded team like the Mets, they still have guys like Endy Chavez, Jose Valentin and Paul Lo Duca. Baseball front offices, regardless of the payroll, should build their teams like baseball teams, not fantasy baseball teams."