Vince held a monstrous $11.6 million cap hit for the 2014 season and cutting him would have freed up over $8 million in space.
By restructuring, the Patriots are able to retain their defensive captain and spread the cap hit from his contract over three seasons. In all likelihood, the Patriots guaranteed Wilfork
his expected money in 2014 $3 million via Ian Rapoport and lowered his cap hits over the upcoming season. He can earn up to $8 million by reaching playing incentives.
The contract structure will likely allow the Patriots to cut Wilfork if he doesn't recover his playing form after 2014, while the cap hit will now be split over multiple seasons.
The Patriots played hardball with Wilfork and allowed him to poke around with other teams to determine his market value before restructuring. Nothing was ever reported about potential interest, which for an agent means that there wasn't much smoke.
We're all glad to have Wilfork back and we'll talk more when the official numbers are released.
Edit: The Herald's Karen Guregian reports that it's really a 1 year deal for $8 million, with $3 million guaranteed, with an option for two additional seasons. We'll have to find out if they're annual options, or a single extension. Per Ben Volin of the Globe, the Patriots will have saved $3.6 million on this year's cap if Wilfork reaches all of his incentives, effectively doubling the room the Patriots have for the rest of the off-season.
Edit2: Per Adam Schefter, Wilfork could have received "more on the open market" but not enough to make him move his family.