Mike Mussina obviously isn't getting any younger, but you certainly wouldn't have noticed that last year. Last year, "Moose" had his only 20 win season in his whole career, and his lowest ERA since 2001. Moose also matched his second highest starts in a year.
All this came in a year in which the Yankees ace Chien-Ming Wang was hurt rounding the bases in interleague play. The Yanks still had lefty Andy Pettitte available, but in a season in which he had 14 losses, and his highest ERA since '99, first year manager Joe Girardi had to turn to someone else.
With Wang out, and Pettitte not performing well enough, the Yankees had to resort to Carl Pavano, and even calling up Kei Igawa briefly. Also, both Ian Kennedy and Phil Hughes were either hurt or disappointments.
This led the way for the 39-year-old Mussina to do well. Mussina was the only consistent and reliable starter for NYY last year, and with the lack of a big free agent landing, this rotation is going to miss his presence.
It's not out of the picture for the Yankees to still land CC Sabathia, Ben Sheets, or AJ Burnett, but Moose's departure certainly doesn't help. The fact that Pettitte is a free agent doesn't help either, and if the Yankees don't land one of these pitchers, they could be in big trouble.