LB to IR; Jackson out vs. Miami

The Atlanta Falcons on Tuesday placed linebacker Sean Weatherspoon on injured reserve, but designated him to return, and announced that running back Steven Jackson will miss Sunday's game against the Miami Dolphins.

Weatherspoon suffered a foot injury in the Falcons' 31-24 Week 2 victory over St. Louis and won't be eligible to return until Week 11 against Tampa Bay.

Jackson suffered a thigh injury Sunday. NFL.com earlier reported the running back may miss two to four weeks, and coach Mike Smith confirmed later Tuesday that Jackson would miss Sunday's game. Smith said Jackson's injury is not expected to keep him out for a significant amount of time.

A league source told ESPN NFL Insider Ed Werder that Jackson will miss three weeks.

"He will not play this week. I know that," Smith said. "It is short term. When I say short term, I don't know if it's two weeks or three weeks, but Steven is ruled out for the game this week and will not play."

Jason Snelling and Jacquizz Rodgers combined to rush for just 36 yards after Jackson's injury, which was apparently suffered after he caught a touchdown pass from Matt Ryan in the first quarter. Snelling rushed for a touchdown. His playing time was already expected to increase because fullback Bradie Ewing was placed on injured reserve Monday with a shoulder injury.

On Tuesday, the Falcons added fullback Patrick DiMarco to the active roster and signed veteran linebackers Jamar Chaney and Omar Gaither.

The Falcons lost linebacker/defensive end Kroy Biermann to a season-ending Achilles injury Sunday, leaving the team thin at linebacker.

Rookies Joplo Bartu and Paul Worrilow are two players likely to receive more playing time.

Weatherspoon, 25, has 10 tackles this season. He finished second on the team with 95 tackles in 2012, when he also had three sacks and an interception.

On Tuesday afternoon, after the Falcons announced he was being placed on IR, he tweeted his thoughts on the move.

He followed that with a tweet that "it gets greater later."

Smith said he hasn't experienced a similar wave of injuries in his six years as Atlanta's coach.

"We've not had anything close to this," Smith said. "There have been games where we've had guys who have not been able to play and it's been the next-man-up mentality, and I think that's really what our guys understand. I tell them all the time we have very defined roles on our team and in our organization, but I tell them on our team those roles can change just like that and you've got to be prepared."

Information from The Associated Press was used in this report.