I would let Mankins play out this year of his contract and cut him next year. My issue with re-structuring Mankins contract is it makes it so much harder to part ways with him next season if his play continues to decline. I don't want a 33 year old LG with a $12.5mil cap hit and $7mil in dead money on the books. He's been a great player for the Pats but I was never a fan of that contract and I would try and get out from under it as soon as I could and 2015 seems like the right time.
From Mankins perspective he would be silly to not accept a re-structure. It would not only give him part of his money upfront but it would also make him much harder to cut next season almost guaranteeing that salary too. If he was offered a pay cut I could see why he would turn it down, but a straight re-structure turning base salary into bonus money is a no-brainer.
Here's the problem:
1.) The story, assuming the source is correct in both cases, doesn't tell us why a Mankins restructure isn't going to happen. It just claims that it's not going to happen. Two likely reasons for it:
a.) Mankins doesn't want it
b.) Patriots don't want it
In the case of (a), it's likely because the Patriots are trying to combine a re-structure with a reduction. After the way they dealt with him before, it would come as no surprise that he'd balk at that.
In the case of (b), it's likely because the Patriots either plan to cut him after this year or to use that threat as leverage. Given the earlier history, this would seem to be far more likely to end up as a release than a lessened contract, but humans can be quirky.
In any case, the reality is that Mankins is the Patriots best offensive lineman, that second place isn't all that close, and that finding a way to keep Mankins in the fold for the next two seasons is probably the smartest move, given the other issues on the line.