Since our last World Championship here are the teams we've lost to:

2001 Diamondbacks
2002 Angels
2003 Marlins
2004 some obnoxious team
2005 Angels
2006 Tigers

The only one of these teams that I thought was better than the Yankees (and by better I mean would beat them 55 games out of 100 or so) was the 2002 Angeles.  On the other hand the only team that was worse in my view was the 2003 Marlins.  I haven't looked up third order Pythagorean records or anything like that.  This is just a rough impression.

Before that we had won 12 out of 13 postseason series from 1996-2000.  What is different? Well for one thing the 1998 and 1999 teams were clearly better than everyone they faced except possibly the 1999 Braves. But that still leaves the question of why did the teams from those 5 years not lose to inferior teams and occasionally beat superior ones?  This is the question Cashman and co. should be pondering. I see several possible explanations none of which are entirely satisfactory.

1. Heart.  A lot of commenters on this and other blogs cite a lack of heart on this team.  I don't see it.  Does anyone think A-Rod doesn't desperately want a title? How about Giambi and Mussina?  No, I think the answer has to be between the lines.
2.  Bullpen.  A great bullpen is often cited as a key in the postseason.  While Mo is a constant between eras, the setup crew has deteriorated.  Still, how many playoff games have the Yankees lost since 2001 because of poor setup men?  It's hard to see this being more than a marginal contributor.
3.  Defense.  The 1996-2000 teams were good defensively, probably better than the 2001-2006 Yanks.  I'd love to see some research on the contribution defense made in the last 6 playoff losses but until I see something concrete, I am skeptical.
4.  Starting pitching.  This is the explanation I most want to believe.  The 1996-2000 teams had Cone and El Duque (and Wells in 1998) who were huge big game pitchers.  Still there are two problems with this explanation.  The 2002 Angels, the best team we've lost to in my view, had very mediocre starters.  And if starters are that important in the postseason, why haven't the Braves won more titles?
5.  Luck.  This is the explanation I keep coming back to.  When two good teams play a 5 or 7 game series, the better one will lose nearly half of the time.  Little things like a Tony Clark ground rule double, or Bubba Crosby and Gary Sheffield crashing into each other or a rainout forcing the Yanks to face Verlander and Zumaya in the shadows can make a determinative difference.