Source: Bills rookie LB Reggie Ragland has partial tear of ACL

An initial MRI shows that Buffalo Bills rookie linebacker Reggie Ragland appears to have suffered a partial ACL tear in his left knee, but the team is confident it is not fully torn, a team source told ESPN NFL Insider Adam Schefter.

The team is scheduled to get a second opinion of Ragland's MRI on Monday, and that will determine how much time the rookie second-round pick will be expected to miss, the source said.

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.

With Ragland's status uncertain, the Bills signed veteran linebackers Brandon Spikes and David Hawthorne on Sunday.

Spikes, 28, last played in the NFL for the Bills in 2014. He signed with the New England Patriots last year but was released in June 2015 as police investigated his role in a hit-and-run crash in Massachusetts. Spikes later pleaded guilty to multiple motor vehicle charges and received probation. The NFL suspended Spikes for the first four games of the 2015 regular season, which he spent out of football.

Hawthorne, 31, played the past four seasons for the New Orleans Saints. Bills assistant head coach/defense Rob Ryan coached Hawthorne from 2013 until the Saints fired him as defensive coordinator during the 2015 season.

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 right shoulder surgery this spring.

Ryan already had named Ragland as the expected starter at inside linebacker alongside Preston Brown.

Information from ESPN Bills reporter Mike Rodak was used.