New York Jets quarterback Aaron Rodgers will miss the rest of the NFL season with a torn Achilles tendon.
The four-time Most Valuable Player sustained the injury just four snaps into his Jets debut.
Rodgers, widely considered one of the best quarterbacks of all time, had spent his 18-year professional career with Green Bay Packers until he asked for a trade in the off-season.
"He's down," said Jets head coach Robert Saleh.
"With everything he has invested and it lasting four plays, you can imagine it's disappointing."
Rodgers will be 40 in December and his NFL future may now be in doubt.
"I did not get into the future of what he's expecting. I'll let him get into those questions," Saleh said.
"We'll try to let him breathe and give him some time to process everything. He has invested so much in this organisation, into this journey he has embarked on.
"It's really all about him. Guys are excited to step up and continue what we have been building but there's a lot of hurting for Aaron."
Zach Wilson, the second overall pick in the 2021 NFL draft who was benched last season, is New York's back-up quarterback and replaced Rodgers against Buffalo Bills.
The Jets went on to win 22-16 in overtime, with Wilson throwing one touchdown and one interception, but their victory was heavily overshadowed by the injury.
Saleh said after the game that the Jets believed Rodgers had a ruptured Achilles, which was later confirmed by an MRI scan.
"Not the way any of us wanted it to go, but we know the commitment you've made to this team will continue to impact us moving forward," the Jets said in a statement, adding: "Get well soon, Aaron Rodgers."
There had been high hopes for the Jets - who have not won their four-team division since 2002 - this season following Rodgers' arrival.
Rodgers won Super Bowl XLV with the Packers in 2011 and his 475 regular-season passing touchdowns are the fifth-most of all time.