A league source confirms that the Patriots have placed six veteran players on their active/physically unable to perform list to start training camp:
TE Jake Ballard
TE Daniel Fells
G Logan Mankins
DL Myron Pryor
LB Brandon Spikes
OT Sebastian Vollmer
Each was dealing with an injury/surgical recovery during the offseason - Mankins and Ballard (then as a member of the Giants) each tore an ACL in Super Bowl XLVI; Spikes underwent knee surgery after the Super Bowl; Vollmer underwent a small back procedure; Pryor had shoulder surgery last year, and Fells is reportedly nursing a leg injury.
They join rookie Jeremy Ebert, who was placed on active/PUP by the team last week.
Players on active/PUP can be removed at any time, though they do count against the 90-man roster.
Rob Gronkowski, who underwent ankle surgery after the Super Bowl, is not on the current list, which can only be taken as a positive - the Patriots must believe that he is good to go.