Broncos head coach Vic Fangio told reporters that Chubb suffered the season-ending injury during Sunday's 26-24 loss to the Jacksonville Jaguars. The coach called the injury a "huge loss" for the winless Broncos.
"He felt good enough to come back in and actually, he played that last series pretty [expletive] well," Fangio said. "[He] had some really good pass rushes, caused that fumble that we weren't able to get. He was as surprised as anybody, I think, this morning when he woke up feeling the way he did.
"It's a huge loss. He's one of our better players, obviously. He's a tempo setter, great player, great person, leader -- all that."
Fangio said Chubb felt discomfort in the knee Monday morning and underwent an MRI, which revealed the ligament damage. The star outside linebacker exited Sunday's game twice due to a calf injury and the knee ailment before returning to the contest.
Chubb sustained the injury with about 14 minutes left when he was engaged with Jaguars tight end Geoff Swaim on a running play. He played 74 of the Broncos' 85 snaps on defense, including all of the team's snaps on the Jaguars' final drive in the closing minutes of the game.
Chubb recorded his first sack and forced fumble of the season against the Jaguars. The 2018 fifth-overall draft pick set the Broncos rookie sack record last season when he notched 12 quarterback takedowns.