Bullpens make or break great teams. The championship Yankee teams of the late 1990's were backboned by the infallible 4 man relief corps of Ramiro Mendoza, Jeff Nelson, Mike Stanton and Mariano Rivera. A very good, if not great bullpen is a prerequisite to postseason success nowadays.
In what many consider to be a slow offseason for the Yankees (after all, they only shelled out $133.35M worth of major league contracts), the area they most improved was their bullpen, which was in need of great repair.
Last season, the Yanks bullpen posted a 4.37 ERA (good for 20th in baseball) and 6.38 Kper9 (23rd). Take out the incomparable Mariano Rivera and those numbers translate to 4.98 and 5.81, respectively. Furthermore, the 21 pitchers the Yankees used in relief last year put up a 1.05 GB/FB ratio (559/531). Again, take out Mo and you've got a .95 GB/FB ratio (447/472). For the sake of having the info in front of me, the Indians pen - best in the business in 2005 - put up a 1.07 GB/FB ratio (502/469).
The 4 main guys the Yanks brought in to help the pen (Farnsworth, Dotel, Myers and Villone) were much more effective as a group last year than the Yanks relief corp (how couldn't they have been). Combined, they put up a promising 3.13 ERA and 9.35 Kper9 to go along with a 1.01 GB/FB (179/178).
You want your relievers (or all pitchers for that matter) to do one of two things: get strikeouts or get groundballs. It seems as if the new guys can at least do one of those things, making the bullpen seem better at least on paper. Where am I going with this? Nowhere really, the stats didn't yield anything interesting as I had hoped they would. Sadly, I'll leave it at that...