Free agent LB Russell Allen suffered a stroke in Week 15 and is being forced to retire.

It was initially believed that Allen suffered a concussion in the Week 15 tilt, but two days later it was discovered that he suffered an on-field stroke. A dead spot in his brain, on his cerebellum, has resulted in the end of his football career. We now know why Allen was released with the failed physical designation last week. The 27-year-old entered the league as an undrafted free agent and never missed a game until the final two of 2013. His career ends with 331 tackles, two sacks, two forced fumbles, and one interception across five seasons.

Jaguars released LB Russell Allen.

The move clears $2.5 million in cap space. A 2009 undrafted free agent, Allen has spent his entire career with the Jaguars, starting 29 games over the past two seasons. The Jags' weak-side linebacker in 2013, Allen tallied 64 tackles and a sack before a concussion sent him to injured reserve in Week 16. He graded out as Pro Football Focus' No. 17 4-3 outside linebacker, playing 533 snaps. Going on 28, he'd be a nice piece of depth for a contending team, and potential starter elsewhere.

Jaguars placed LB Russell Allen on injured reserve, ending his season.

Jaguars OLB Russell Allen left last night's game with a walking boot on his right ankle.

Allen was injured on the first play of the game. There are no further details at this time, but if Allen was to miss any time, the Jags will look to Julian Stanford or Brandon Marshall to step up.

Russell Allen and Geno Hayes are penned in as the Jaguars' starting outside linebackers.

The Jags let voncussion-riddled Clint Session go during last season and Hayes was their only significant free agent addition at linebacker. They didn't spend any draft picks at the position. Middle linebacker Paul Posluszny and Allen are tackle machines, but are far from run-stuffers. The Jags' defense will be one for fantasy owners to attack once again this season.

The Florida Times Union expects Russell Allen to challenge Clint Session for the Jaguars' starting weak-side linebacker job.

Allen is at worst the Jaguars' top backup at all three linebacker positions, and he held his own in six spot starts last season. With a new coaching staff in Jacksonville, Session's $29 million contract no longer carries as much weight in camp battles. Session was concussed three times last year.

Jaguars agreed to terms with LB Russell Allen on a three-year contract.

A restricted free agent, Allen was tendered at the second-round level just prior to agreeing on the new deal. The Jaguars value Allen highly after he held his own while filling in for Phillip Wheeler late last season. Allen will return to a reserve/special teams role in 2012.

The Jaguars are attempting to work out a multi-year deal with restricted free agent LB Russell Allen.

Allen has appeared in all 48 games since signing as an undrafted free agent in 2009, making 15 starts. He played 293 snaps in 2011, grading out positively against the run and in coverage by Pro Football Focus.

Russell Allen is expected to replace Clint Session (injured reserve, concussions) in the starting lineup.

Allen, a former undrafted free agent, will step in on the weak side. He started four games at outside linebacker last season, piling up 42 tackles.