26-year-old NFL player who has made $29 million is retiring for a second time because of concussions
Davis previously shocked the NFL world when he announced his retirement prior to the 2015 season, only to attempt a comeback this season.
When Davis announced his retirement in June, 2015, he stated that wanted to give his "brain and body a chance to heal." At the time he left open the possibility of a return to the NFL.
After returning to action this season, Davis suffered a concussion in practice. As a result, he was sidelined for the 49ers' last two games.
David has already made $29.2 million in his career. However, by retiring in 2015, he walked away from $23 million remaining on the five-year, $33.2 million extension he had signed prior to the 2013 season.
Davis started every game in his first four seasons after being the 11th pick of the 2010 draft. However, he missed nine games in 2014 because of a concussion as well as multiple leg injuries.
Davis is part of a growing trend in the NFL of players retiring at young ages. In 2015, 19 players aged 30 or younger retired from the NFL. That was up from just five players in 2011.