49ers take yet another hit as right tackle Anthony Davis retires at 25

What is going on in San Francisco that is causing this mass exodus from the 49ers?

The 49ers had another shocking retirement, as starting right tackle Anthony Davis announced he is stepping away from the game. Davis was a first-round pick in 2011, an immediate starter for the team and has started all 71 games he played in. He is 25 years old.

Davis suffered a concussion last season, and he referenced healing his brain in his announcement. Here's Davis' statement, via ESPN's Adam Schefter:

"After a few years of thought, I've decided it will be best for me to take a year or so away from the NFL. This will be a time for me to allow my Brain and Body a chance to heal. I know many won't understand my decision, that's ok.

"I hope you too have the courage to live your life how you planned it when day dreaming to yourself growing up. Your Life is Your dream and you have the power to control that dream. Im simply doing what's best for my body as well as my mental health at this time in my life."

Last season, Davis explained to the San Jose Mercury News that after he suffered a concussion on Nov. 16 against the New York Giants, his symptoms were severe and lasted a long time. He said he saw a "white fog" and had trouble maintaining conversations. Davis returned for the 49ers' final two games in late December. That was Davis' first concussion.

"It's scary when your brain is not working how it's supposed to," Davis told the Mercury News last year, "and the culture of this league is, 'You're a big, tough guy.'"

Pro Football Talk reported Friday that Davis will pay back some bonus money:

Davis left open the possibility of returning to the NFL in his statement, but it's still another brutal blow for the 49ers.

San Francisco parted ways with coach Jim Harbaugh immediately after last season. Since then, running back Frank Gore, receiver Michael Crabtree and guard Mike Iupati were among those to leave via free agency. Linebackers Patrick Willis and Chris Borland unexpectedly retired. Defensive end Justin Smith also retired after contemplating a return for another season.

All of these issues could just be a really rough coincidence for the 49ers. But no matter, they've lost a ton of talent for one offseason.