Personally I don't sell Wilfork short based on age, except insofar as it factors into recovery from injury. I agree that he was likely playing with some degree of Achilles' impairment, which would explain exactly why Vlad Ducasse was able to push him around. I discount his play during the first 4 games of the season.
What I don't discount is Wilfork's ability to come back and play like he did from 2004-2012. His age, weight, and significant family history of diabetes are all medical factors affecting his ability to recover. Without a full recovery of his Achilles' tendon he'll be unable to push off with any force and will be playing on skates. What I suspect we'll end up getting is Wilfork more like he was during the first 4 games of this season than the old Wilfork, if he comes back at all. That's what scares me, along with the fact that he'll be at some risk for re-injury given his age, weight, family history of diabetes, and the ridiculous stress loads that he would be subjected himself to.