Crawford suffered the injury during Atlanta's 23-17 loss to the Buffalo Bills on Sunday. He played 12 defensive snaps in the game as a reserve.
Losing Crawford further depletes the Falcons' depth along the defensive line. Pass-rusher Vic Beasley Jr. (hamstring) and defensive lineman Courtney Upshaw (ankle/knee) are working their way back from injuries. The Falcons released former second-round pick Ra'Shede Hageman, the backup nose tackle, after an investigation into a domestic incident.
Falcons coach Dan Quinn expressed optimism about Beasley returning soon, once he can open up and run without issue. The reigning NFL sack champ was expected to miss a month after suffering a hamstring strain against Green Bay on Sept. 17.
Upshaw's status is a little less clear, although he won't need surgery, Quinn said. Upshaw was not on the field doing rehab exercises alongside Beasley last week.
As for Crawford, who formerly played for the Dallas Cowboys, he has brought versatility, power and toughness to the defensive line, primarily from the interior. He was limited some during the preseason while dealing with a groin injury. Once Crawford was healthy, he provided backup support to interior lineman Grady Jarrett and Dontari Poe. Through four games, Crawford recorded five combined tackles and three quarterback hits.
Joe Vellano, who was promoted from the practice squad after Upshaw's injury, is the primary backup now on the interior of the defensive line. Derrick Shelby, who has lined up at defensive end while Beasley is sidelined, also can play inside.
The Falcons did not immediately announce a corresponding roster move after placing Crawford on IR, but Quinn said Monday he would meet with general manager Thomas Dimitroff about adding help along the defensive line. The Falcons worked out six defensive linemen Monday: Sterling Bailey (Georgia), Pat O'Connor (Eastern Michigan), Devin Taylor (South Carolina), Nicholas Williams (Samford), Jonathan Woodard (Central Arkansas) and Lavar Edwards (LSU). O'Connor was informed he won't be signed at this time.
The Falcons (3-1) have a bye this week as players rest and recover from injuries. Their next game is Oct. 15 at home against the Miami Dolphins.