Durability has pretty much defined A.J. Pierzynski's career. Since 2011, he has played 100+ games in each season and has not missed significant time due to injury. Pierzynski has made his money on this, relying on the fact that he can give a team 100-150 of near-starter level catching. Unfortunately, like I said, it's only near-starter level; he has only had four years (2002, 2003, 2006, and 2012) that resulted in 2.0+ fWAR, the former two being ten years ago. Only two of those years (2003, 2012) were of the 3.0+ fWAR variety. One of them was last year, so it is possible that there is something left in the tank.
All of Pierzynski's game is reliant upon his defense; according to Fangraphs' fielding and positionally adjusted defense stat, he has compiled 99.6 defensive runs above average in his career. His hitting is below-par at a career 94 wRC+ line, and has had only one 100+ wRC+ year (2012) since 2003. Overall, according to Fangraphs' offense stat, he is at a career 91 runs below average. There's a possibility he could up his HR/FB% by playing in Yankee Stadium, but I wouldn't bet on that with his age. That combined with pretty poor base running, Pierzynski's bat is merely put up with at the bottom of the order.
That all being said: the Yankees do, in fact, need a catcher. And by need, I mean that if Chris Stewart is in the opening day lineup, things will be broken. But I also believe that there is no use in picking from the bottom of the free agent pool this early, especially picking a player who will be 38 in the spring and who isn't cheap either; $7.5 million in 2013 is no bargain for someone like that. There are other options as of right now, Dioner Navarro and Brian McCann, and I think those two should at least be aggressively pursued before acquiring Pierzynski.