There's a huge difference between a first string catcher who can't hack it any longer and, having lost the starting catcher for an indeterminate time and having the third and fourth string catchers out of spring training be on the DL at Pawtucket then losing the backup, thus leaving you with a fifth string catcher and a career minor leaguer to try to hold down the fort. On top of that, there is a level of comfort between certain pitchers and Varitek (Dice-K, Beckett, Buchholz) which is now gone.
How would you feel if the Yankees lost Posada, Cervelli, and the next two catchers on the depth chart? Even with the depth the Yankees supposedly have, I suspect you'd be mighty worried if the fifth best catcher in the system was going to be a full time starter.