The Atlanta Falcons are expected to be without reigning NFL sack leader Vic Beasley Jr. for at least a month because of a right hamstring tear, a league source confirmed to ESPN.

Falcons coach Dan Quinn did not put a timetable on Beasley's hamstring, which he called a "strain.''

"We certainly won't put that kind of timeline on him. ... I know he's a guy who's going to work really hard at it," Quinn said. "I know he'll miss this week. And past that, we'll see where it goes, if he's able to make it back in time for the next game [home vs. Buffalo, Oct. 1], and then we have a bye. So we'll see where it goes.''

Quinn ruled out Beasley along with defensive lineman Courtney Upshaw (ankle) for next Sunday's game at Detroit after both underwent MRIs on Monday.

Quinn went on to say that rookie first-round draft pick Takk McKinley would be first up to replace Beasley rushing off the left edge, followed by Brooks Reed and Derrick Shelby.

"I did both in college, and when I got here, it was mostly right," McKinley said. "I'm pretty sure in practice I had a few reps on the left side. It's just getting back adjusted and getting ready to rush on both sides."

Quinn said there is no immediate plan to add a pass rusher to the 53-man roster but also said the Falcons remain in contact with seven-time Pro Bowler Dwight Freeney, who was with the team last season on a one-year deal but wasn't immediately re-signed.

"Yes, definitely somebody that we still talk to on a regular basis,'' Quinn said of Freeney. "We're hopeful that he's going to play this year, and I'm really certain he wants to. But right now, no changes on our end.''

Beasley was injured during Sunday's 34-23 win over the Green Bay Packers. He exited the field under his own power early in the third quarter but was visibly upset and screaming, obviously aware that the injury was somewhat significant.

Beasley, who had a league-high 15.5 sacks last season, has two sacks, two quarterback hits and a forced fumble that was returned by teammate Desmond Trufant for a touchdown through the first two games.

The news regarding the length of Beasley's injury was first reported by WSB-TV Atlanta.

Veteran Adrian Clayborn, who rushes only off the right edge, applied consistent pressure on Rodgers and collected a sack. He's a player the Falcons might need to rely on for pressure in the next few games.

"I play one way, and I just do my job," Clayborn said. "That's all I know what to do."

Strong-side linebacker De'Vondre Campbell, who recorded his first career sack against the Packers, might be another option in the group of edge rushers.

Another option for the Falcons would be promoting rookie J'Terius Jones from the practice squad. He impressed Quinn during the preseason.

If Beasley is sidelined only a month, he would miss games against the Detroit Lions, Buffalo Bills, and Miami Dolphins but possibly return for the Super Bowl rematch against the New England Patriots on Oct. 22.

"Vic works his butt off," Reed said. "He's definitely a guy that we need."