The four-time Pro Bowl lineman can be removed from the list at any time. He underwent surgery in February to repair a torn ACL in his left knee, and reports had varied on whether Mankins would be able to return for the start of training camp.
At this point, his placement on the active/PUP list likely means that Mankins will not be ready to practice when the team opens camp on Thursday. However, the team has more than a month before it would have to make a decision on whether to place Mankins on the reserve/physically unable to perform list, which would keep him out for at least the first six weeks of the season.
Tight end Rob Gronkowski (ankle) was among the injured veterans reporting to Gillette Stadium on Monday. He was not placed on the active/PUP list, a positive sign for his availability for the start of training camp on Thursday.