The Falcons confirmed Allen's injury on Monday and will play the rest of the season without their starting safeties. Strong safety Keanu Neal suffered a season-ending knee injury in Week 1 at Philadelphia.
Allen was injured in the Falcons' 43-37 loss to New Orleans. During the game, the Falcons announced Allen had a calf injury.
Allen signed a three-year $19.5 million contract extension over the offseason. He is considered the leader of the defense, and his long-term loss likely will be significant for the team.
The Falcons defense also has been playing without linebacker Deion Jones (foot), defensive end Takk McKinley (groin) and defensive end Derrick Shelby (groin).
"Yes, (general manager) Thomas (Dimitroff) and I discussed that, and we'll continue to discuss that afterward," Quinn said. "We have some other guys with some versatility that we'll try to lug around. We'll see what the length of the injuries is. That would certainly make a difference if we went outside to look for somebody else."
However, Quinn said Monday that the team is not planning to add a starting-caliber safety, which would seem to rule out signing free agent Eric Reid or trading for Seattle Seahawks safety Earl Thomas. Quinn said the team is confident in reserve Damontae Kazee at free safety and the duo of Jordan Richards and Kemal Ishmael at strong safety.
Quinn had previously mentioned Reid as a possible option after Neal's season-ending injury.