Possible, he hurt his ACL against Miami and then either reinjured or just played through it in the SB, February isn't that long ago. It's actually sounding pretty likely.
Per Rotoworld: Some ESPN speculation suggested Mankins would head to PUP for the start of the season. Per Curran, Mankins is likely to open training camp on "active/PUP," but should be activated from the list ahead of the opener. Per Curran, Mankins' progress "was termed as 'awesome'." It's very good news for New England, obviously. Mankins has been to three straight Pro Bowls and was a 2010 All Pro.
Not that losing a guy like that doesn't hurt, but they seem to have so much depth on the line and are so good at game planning around weaknesses that I doubt it'll affect the bottom line that much. Unfortunately.