Evan Silva of Rotoworld.com did point out that Allen suffered a concussion in 2010 and 2011. But once again he indicated he’s not retiring because of any health concerns.
If Allen isn’t retiring because of health reasons, I’m not sure why he’s walking away from the game at the age of 24. With the Vikings being thin at the cornerback position, he was in line for a lot of playing time in 2012. So to me it just doesn’t make sense.