Buffalo Bills defensive end Shaq Lawson was placed on injured reserve on Tuesday and will miss the remainder of the season after suffering an ankle injury in Sunday's loss to the New England Patriots.
The Bills also announced that receiver Jordan Matthews is done for the season with a knee injury.
Lawson, a first-round pick in 2016, has 33 tackles and a team-leading four sacks this season.
Defensive coordinator Leslie Frazier said the loss of Lawson is a big blow for the defense.
"You hate to lose Shaq Lawson," Frazier told reporters. "He's done a really good job for us. He's improving and he needs those snaps. In a lot of ways, this is new territory in some ways in our defense, so you want him to get as many snaps as he can get."
Matthews has 25 receptions for 282 yards and one touchdown. He began dealing with knee issues in November and missed the Nov. 19 loss to the Los Angeles Chargers.
He returned to play in the past two games but was limited. Matthews had one catch for 14 yards against the Patriots.
Matthews will be a free agent after the season.
Buffalo promoted defensive end Cap Capi and receiver Brandon Reilly from the practice squad to fill the roster openings.
Capi has played in four NFL games, all with the New York Giants earlier this season. Reilly has been on Buffalo's practice squad all season.
The Bills also signed safety Dean Marlowe and punter Cory Carter to the practice squad.