The Facts: Cameron could keep playing in the NFL if he wanted. But after four concussions and countless hours thinking about the future for himself and his son, Cameron realized it was time to retire. "I started thinking about concussions too much," Cameron, 28, told ESPN on Friday. "You can't play football like that."

Diehards Line: Cameron spent six seasons in the NFL: four with the Browns and two with the Dolphins. His final concussion came in a Dolphins win over the Browns in September; his last play was when he tried to make a tackle after an interception. Cameron joined the NFL when he was drafted out of USC in the fourth round by the Browns in 2011. He had his first concussion in December 2012 and his second against the Bears in December 2013 -- the same year he went to the Pro Bowl and had 80 catches and seven touchdown receptions.