As expected, Mankins, a restricted free agent who has yet to sign the Patriots' one-year tender offer, was not present for the opening day of training camp Thursday at Gillette Stadium. Mankins is seeking a long-term contract and, with the sides unable to come to agreement during the offseason, he demanded a trade in June.
"I've been there and it's a tough for him, a tough one," said Wilfork, who sat out portions of last year's voluntary minicamp to express his displeasure in not having a contract extension, but was present for the first day of training camp. Wilfork played out the final year of his contract and signed a five-year extension this offseason.
"We miss him out here. Like I said, I back him 110 percent. He's the best offensive guard out there. I see this guy every day. I see his work, the type of person he is. But business is business and you have to respect both sides. I'll leave it at that. He's a great athlete, a great player, but business is business and you have to let business take care of itself."
Asked about Mankins before the morning session, Patriots coach Bill Belichick said only: "All of the players that are here are under contract, and Logan is not under contract."
Mankins hadn't missed a practice since being plugged in at left guard on the first day of training camp in 2005. The two-time Pro Bowler was replaced among the starters by Nick Kaczur Thursday, but his absence resonated with teammates.
"I stay out of all that stuff," left tackle Matt Light said. "Every guy has gone through a contract situation, whether it's coming in and signing as a rookie or being a guy that's going into your second or third contract. We've all faced it and we know that it's part of the game. It's unfortunate. The only thing I'll say to that situation is he's a great teammate and he's always been a great teammate. He's a guy who's never missed a game and we definitely miss not having him out here."
Burgess, a nine-year veteran, is contemplating retirement, sources told ESPN.com's Len Pasquarelli on Thursday.
Welker, not in uniform, participated in strength and conditioning work on his own, while Aiken, Jenkins, and Brace all were spotted on the sideline in sweats.
Chris Forsberg is the Celtics reporter for ESPNBoston.com who's checking in from Patriots training camp this week. Follow him on Twitter.