Davis addressed his retirement in a tweet, writing:
Davis returned to the 49ers just before the start of training camp after taking the 2015 season off to, as he said, "allow my brain and body a chance to heal." Upon his return, Davis was unable to win back the starting right tackle job from Trent Brown and moved inside to right guard before the team's second preseason game against Denver.
Heading into the regular season, Davis had seemingly won the starting right guard job, but coach Chip Kelly decided to go with Andrew Tiller at that spot before the season opener against the Los Angeles Rams. Davis missed a practice the Saturday before the opener amid reports he was again considering retirement, but Kelly and Davis called it a "miscommunication" that they went on to resolve.
Davis ended up serving as the team's primary backup tackle and played three snaps late in the 28-0 win against the Rams. Then, just three days before the Niners' Week 2 game against Carolina, Davis was diagnosed with a concussion that prevented him from traveling and playing in that game.
Kelly said last week he didn't talk to Davis after he suffered the concussion because the team traveled to Carolina on Friday.
"I haven't seen AD since Thursday, so we'll see where he is with it and what's going on," Kelly said then. "And obviously, he'll go into the league concussion protocol and we'll go through all the process there. There's a system in place to make sure that he's not going to be put in harm's way, so we'll see how that goes."
Davis remained in that concussion protocol through last week and was again a pregame inactive for Sunday's game in Seattle.
The 49ers originally selected Davis with the 11th overall pick in the 2010 NFL draft. He quickly claimed the starting right tackle job and went on to appear in 72 games with 71 starts.
Davis previously retired in June 2015 after an injury-plagued 2014 season in which he dealt with shoulder, knee, ankle and hamstring injuries in addition to a concussion that limited him to seven games.
When Davis returned to the Niners in July, he earned positive marks from coaches and teammates for coming back more than 30 pounds lighter than he'd been in the 2014 season. He said at the time that he didn't regret walking away for the 2015 season.
"I didn't miss it right away," Davis said in July. "I had a lot of work to do on my mind and body, so I knew it wasn't ready to come back and play, so missing it wouldn't have done me any good."