ATLANTA — Falcons fullback Ovie Mughelli’s season is over.

The Falcons say they are placing Mughelli on injured reserve. Mughelli hurt his right knee in the fourth quarter of Sunday’s 23-16 win at Detroit. He suffered the injury when hit by Lions defensive back Louis Delmas.

The Falcons also placed backup offensive guard Mike Johnson on injured reserve with a foot injury on Tuesday.

The Falcons, on their bye week, signed running back Mike Cox and offensive lineman Kirk Chambers.

Cox, from Georgia Tech, played for Kansas City the past three seasons. Chambers, from Stanford, has not played in the NFL since 2009. He played with Cleveland and Buffalo from 2004-09.

Coach Mike Smith said Monday that Jason Snelling would move up at fullback if Mughelli’s injury was serious.

In other NFL news:

Stafford questionable for Sunday

DETROIT — Lions quarterback Matthew Stafford is listed as day-to-day with a sprained right ankle, but on Tuesday he sounded slightly less optimistic about his chances of playing Sunday against the Denver Broncos than coach Jim Schwartz did Monday.

“I think every competitor plans on playing,” Stafford said during a radio interview on Tuesday.

“We’ll see if that comes true. I’ve got to keep getting better to get there, but I want to, obviously.”

Stafford, the former UGA star, hurt his ankle on the Lions’ final offensive play of Sunday’s 23-16 loss to the Falcons, when linebacker Curtis Lofton rolled into his right leg.

Stafford said the sprain is “kind of in a weird spot.

He said he’s not sure whether he’ll practice today. If he can’t play against the Broncos, Shaun Hill, who started 10 games last year, will start.

“We’re treating it, doing the best we can, trying to get it as healthy as possible for a chance to try and play this week,” Stafford said on the radio.

Stafford missed 13 games with two separated right shoulders last year but has played every snap this year, except for two mop-up series in the blowout of the Kansas City Chiefs.

“You sit there and you think, ‘Man, I make it through the whole game, and then on the last play of the game, I’m rolling out, I’m not even in the pocket, and a guy just falls funny on my foot,’” Stafford said.

“You just never know in this league, and that’s understandable, but I’m doing everything I possibly can to get back.”

Notes: The Lions signed defensive back Don Carey on Tuesday. Carey worked out for the Lions last week.

He was released by the Jacksonville Jaguars in September. The Lions had not announced a corresponding roster move as of Tuesday.

The team also signed defensive back Don Carey and released tight end Joe Jon Finley. They also released running back Matt Clapp from the practice squad and re-signed tight end Nathan Overbay to the practice squad.