SAN FRANCISCO (AP) - The NFL is investigating whether Buffalo defensive end Mario Williams has an injured left wrist.

Williams has not been on the Bills' injury report this season despite what he claims has been a wrist injury that has bothered him all season. But the team says he has not missed any practices or game time.

NFL spokesman Greg Aiello said Sunday that "the club says he is not injured. We will follow up this week to obtain a formal explanation.''

Williams is the highest-paid defensive player in NFL history, signing a $100 million contract as a free agent in the offseason. He has not played well for Buffalo and has just one and a half sacks.