Davis sat out last year in part because of concerns over a concussion before deciding to return to the Niners this summer. He suffered another concussion in practice Sept. 15 and did not play again before the team announced his retirement Monday.
Davis was slated to start at right guard but missed the final practice before the season opener for non-injury reasons. He then became the backup swing tackle but got hurt before he could play again.
Davis was a first-round pick in 2010 and a key part of San Francisco's three straight trips to the NFC title game from 2011 to '13.