PITTSFORD, N.Y. -- Buffalo Bills coach Rex Ryan struck a less optimistic tone Saturday about a left knee injury to rookie linebacker Reggie Ragland, backing off his belief that Ragland avoided ligament damage when he was hurt in Friday's practice.

"I'm not real sure [about ligament damage]," Ryan said. "I guess I was just so hopeful there's not going to be ligament things. My understanding is that as you get going, your leg is so tight, they'll fight it. You don't really get a true look of that. So as we mentioned, we got to wait for that swelling to go down.

"I know every Bill fan out there is hoping for the best, and that's certainly what we're doing, but there is concern."

A source said that more could be known about the severity of Ragland's injury as soon as Sunday. With uncertainty over Ragland's availability, Ryan said the Bills will work out free-agent linebackers Sunday, although he did not identify which players would be visiting.

Ragland, the Bills' second-round pick in April's draft, was pursuing running back Reggie Bush toward the sideline on a play during Friday's practice when he pulled up limping and immediately went to the ground.

Buffalo Bills coach Rex Ryan said "there is concern" about the extent of rookie linebacker Reggie Ragland's left knee injury, and that the team will bring in and work out free-agent linebackers. AP Photo/Bill Wippert

"It just looked odd," Ryan said Friday. "It wasn't hit. None of that stuff. So sometimes those can be the worst ones, so I'm hoping -- we just have to keep our fingers crossed and hope he's fine."

The Bills traded up to select Ragland with the No. 41 overall selection. General manager Doug Whaley said the team considered selecting the Alabama linebacker with its No. 19 pick in the first round, but Buffalo drafted Clemson defensive end Shaq Lawson instead.

Lawson is expected to miss the first several games of the regular season after undergoing shoulder surgery this spring.

Ryan already had named Ragland as the expected starter at inside linebacker alongside Preston Brown. Veteran Zach Brown replaced Ragland with the first-team defense for the remainder of Friday's practice.

"I'd rather not think about it, but we're in capable hands," Ryan said of the possibility of losing Ragland for an extended period. "We have a couple of pretty good inside 'backers, guys that are doing well right now -- Zach Brown and Randell Johnson -- so one guy would have to step up."

In addition to Ragland, the Bills also are dealing with injuries to inside linebackers Kevin Reddick, who Ryan said Saturday is expected to miss multiple weeks, and Jamari Lattimore, who Ryan said could return as soon as Monday.