It was more than a mild surprise when the Jacksonville Jaguars quietly released 27-year-old starting linebacker Russell Allen after five seasons.

It wasn't an upset to Allen, who entered the NFL as an undrafted free agent and was cut three times before. That's because, as he told the Sports Illustrated website, Allen's health will not allow him to continue his professional football career.

Allen said he suffered a stroke on the field Dec. 15, 2013, in a Week 15 game against the Buffalo Bills. He hit center Eric Wood "dead center" while pursuing the ball, and walked away "buzzed."

In the interview with, Allen said that he has a dead spot on his cerebellum about the size of a dime and is still having coordination problems. He will be on blood-thinning medication the rest of his life.

He signed with the Jaguars as an undrafted free agent out of San Diego State in 2009 and started 44 games -- including 29 the past two seasons -- before his release by the team last week. He recorded 452 tackles, two sacks and three fumble recoveries in his five-year NFL career.

Allen thanked everyone for their love and support through his Twitter account @RussellAllen50 on Tuesday, then following it up with this tweet: "I told my story so athletes understand you can't ignore head injuries. If you're not sure you have one, then you do. Report it immediately."