Panda's OPS in the last 4 seasons:
2011: 909
2012: 789
2013: 758
2014: 739
If that isn't a trend in the wrong direction, then i don't know what is. Sure, he's dynamite in the playoffs, but that doesn't mean jack s*** if he can't help you get there.
Also, no matter what, a 6 year-deal for a guy with that body type has a significant chance of turning into an albatross quickly. If i had to choose one of the FA 3B options, i'd go with Headley, who's the righty bat with better D and on-base ability, and i've laready made my thoughts about him being cooked well known, so that gives you an idea about my interest in Panda.