Carolina Panthers quarterback Cam Newton has been ruled out for the rest of the season with a foot injury.
Newton has not featured since the Panthers' week two defeat by Tampa Bay Buccaneers in September having initially suffered the injury during pre-season.
Panthers general manager Marty Hurney said it was "impossible" to put a timescale on his recovery.
"Nobody is more frustrated with that fact than Cam," said Hurney.
"He's one of the fiercest competitors I've been around during my 20-plus years in the league.
"He saw two foot specialists last week who agreed that he should continue that path prescribed by the team's medical staff, and that it likely will take significant time for the injury to fully heal."
Kyle Allen will remain the team's starting quarterback in Newton's absence, starting with Sunday's visit to the Green Bay Packers.
The Panthers (5-3) are second in the NFC South, behind the New Orleans Saints (7-1).