In 2015, Anthony Davis, once a first-round pick of the San Francisco 49ers, announced his retirement from the NFL, stating at the time that he wanted to "let his brain and body heal." Davis un-retired in July 2016, but would re-retire that September, explaining that his decision was again related to potential brain issues that could be brought about by playing football. 

After nearly three seasons away from the game, Davis, now 29 years old, is attempting to return. 

Pro Football Talk received a copy of Davis' reinstatement request letter, and a portion of it reads as follows: 

"On January 24, 2019, I read articles by 3 different sources pertaining to there being a significant decrease in concussions in the NFL, down by 29 percent in the 2018 season. Excited to see that the changes you and your staff have made to the rules, and the allowance of safer equipment to be worn has had a positive effect, I confided with my family and on January 28, 2019 I made the decision that I'd love to play in the NFL again."

Davis wrote that he waited to apply for reinstatement because of his prior use of CBD (Cannabidoil), but that he voluntarily entered a drug testing program and has had no failed tests, missed tests or other issues in 92 days.

"I understand that playing in the NFL is a privilege and I have matured to a point in my life where I am prepared to represent myself, the NFL, and my family with the utmost class, respect and professionalism," he wrote, per PFT. "I appreciate the strides the NFL is making to protect players and better the game for all. I also appreciate this opportunity and I do not take this for granted."

If Davis is reinstated by the league, the 49ers will control his contractual rights. They drafted right tackle Mike McGlinchey in the top 10 last season and still have Joe Staley entrenched at left tackle, so it's possible they will either keep Davis on as a backup tackle, move him inside to guard, or release or trade him so he can seek employment elsewhere.