The 2016 season for one of the NFL’s top wide receivers is ruined before it truly began.

A source told Sporting News that San Diego wide receiver Keenan Allen tore his right ACL during the second quarter of Sunday’s game at Kansas City.

MORE: Week 1 picks against the spread | Straight-up picks

The official confirmation is expected following medical testing.

Allen’s knee buckled while he was cutting on a pass route. He was taken off the field on a cart and ruled out of the game.

MORE: NFL Week 1 live updates

It was Allen’s first game back since missing the final eight contests last season with a lacerated kidney. Allen, 24, had 67 receptions for 725 yards and four catches at the time of his injury, marking the third-highest catch total in NFL history through the first eight games of a season.

Allen, the 2013 NFL Offensive Rookie of the Year, signed a five-year, $46.7 million contract extension in June that included $20 million guaranteed.