The Jaguars will be without a defensive starter for the first time this season when the team hosts the Indianapolis Colts Sunday.
Weak-side linebacker Telvin Smith (concussion) has been ruled out of the Week 13 matchup.
Smith suffered a concussion during the first half of the Jaguars' Week 12 loss to the Arizona Cardinals. Due to the league's concussion protocol, he was held out of practice throughout the week.
This will be the third missed game of Smith's career. He missed two games in 2015 due to injury.
With the veteran sidelined, rookie Blair Brown will play on the weak side in base formations. Starting middle linebacker Paul Posluszny will take on Smith's responsibilities in nickel coverage.
Wide receiver Allen Hurns (ankle) and offensive tackle Josh Wells (concussion) were also ruled out for Sunday's game.
Hurns has missed the last two games with an ankle injury. He has been replaced in the lineup by the rookie combination of Dede Westbrook and Keelan Cole. That duo is likely to cover for Hurns again this weekend against the Colts.
Wells was a late addition to the injury report Friday. The swing tackle suffered a concussion this week and is currently in the league's protocol.
Wells started the last three games in place of right tackle Jermey Parnell (knee), who has been sidelined due to injury. Parnell is listed as questionable but is likely to return to the lineup after participating in practice throughout the week.
With Wells sidelined, backup lineman Josh Walker is likely to serve as the team's swing tackle against the Colts.
Starting left guard Patrick Omameh has also been listed as questionable with a quad injury. He has been replaced by Chris Reed at over the last two weeks. If Omameh can't play, Reed would seemingly fill in at left guard again.
Special teams ace Lerentee McCray has also being listed as questionable with a hamstring injury.
Full Jaguars Injury Report for Week 13:
OUT: WR Allen Hurns (ankle), LB Telvin Smith (concussion), OT Josh Wells (concussion)
Questionable: RT Jermey Parnell (knee), LG Patrick Omameh (quad), LB Lerentee McCray (hamstring)
Follow Mike Kaye on Twitter at @Mike_E_Kaye.