JACKSONVILLE, Fla. — The Jacksonville Jaguars have placed cornerback Derek Cox on injured reserve with a knee injury, the third defensive starter lost in the last two weeks.

The Jaguars made the move Friday, three days after linebacker Clint Session was placed on IR following a second concussion this season. The team also lost cornerback Rashean Mathis to a season-ending knee injury nearly two weeks ago.

The team signed quarterback Dan LeFevour off Indianapolis’ practice squad to take Cox’s roster spot.

Cox, who has 16 tackles and 10 passes defended this season, is the 17th player the Jaguars (3-7) have placed on IR this season.

Making matters worse for Jacksonville, which hosts Houston on Sunday, is both defensive linemen Terrance Knighton and Matt Roth have been ruled out. Aaron Kampman is questionable.

Jacksonville running back Maurice Jones-Drew is doubtful for Sunday’s game against Washington. (John Raoux/The Associated Press)

Jacksonville Jaguars running back Maurice Jones-Drew missed a third consecutive day of practice, casting doubt about his availability against Washington.

Jones-Drew was listed at doubtful on Friday’s injury report, but coach Jack Del Rio declined to reveal whether he expects his star to try to play against the Redskins.

Del Rio says the Jaguars are “going to monitor his condition throughout the weekend.”

Jones-Drew has dealt with knee problems most of the season, but his right one really became problematic after his sixth consecutive 100-yard game, Dec. 12 against Oakland.

He missed two days of practice last week, and Indianapolis held him to 46 yards on the ground.

He sat out practice Wednesday, Thursday and Friday this week.

Updated Dec 24, 2010 2:29 PM ET

JACKSONVILLE, Fla. (AP)

Jacksonville Jaguars running back Maurice Jones-Drew has missed a third consecutive day of practice, casting doubt about his availability against Washington.

FOXSports.com NFL insider Jay Glazer was the first to report that Jones-Drew would likely miss Sunday’s game.

Jones-Drew was listed at doubtful on Friday’s injury report, but coach Jack Del Rio declined to reveal whether he expects his star to try to play against the Redskins.

Del Rio says the Jaguars are ”going to monitor his condition throughout the weekend.”

Jones-Drew has dealt with knee problems most of the season, but his right one really became problematic after his sixth consecutive 100-yard game, Dec. 12 against Oakland. He missed two days of practice last week, and Indianapolis held him to 46 yards on the ground.

He sat out practice Wednesday, Thursday and Friday this week.

Updated Dec 24, 2010 2:29 PM ET

JACKSONVILLE, Fla. (AP)

Jacksonville Jaguars running back Maurice Jones-Drew has missed a third consecutive day of practice, casting doubt about his availability against Washington.

FOXSports.com NFL insider Jay Glazer was the first to report that Jones-Drew would likely miss Sunday’s game.

Jones-Drew was listed at doubtful on Friday’s injury report, but coach Jack Del Rio declined to reveal whether he expects his star to try to play against the Redskins.

Del Rio says the Jaguars are ”going to monitor his condition throughout the weekend.”

Jones-Drew has dealt with knee problems most of the season, but his right one really became problematic after his sixth consecutive 100-yard game, Dec. 12 against Oakland. He missed two days of practice last week, and Indianapolis held him to 46 yards on the ground.

He sat out practice Wednesday, Thursday and Friday this week.

JACKSONVILLE, Fla. – Jacksonville Jaguars running back Maurice Jones-Drew has missed a third consecutive day of practice, casting doubt about his availability against Washington.

Jones-Drew was listed at doubtful on Friday’s injury report, but coach Jack Del Rio declined to reveal whether he expects his star to try to play against the Redskins.

Del Rio says the Jaguars are “going to monitor his condition throughout the weekend.”

Jones-Drew has dealt with knee problems most of the season, but his right one really became problematic after his sixth consecutive 100-yard game, Dec. 12 against Oakland. He missed two days of practice last week, and Indianapolis held him to 46 yards on the ground.

He sat out practice Wednesday, Thursday and Friday this week.