SANTA CLARA (AP) — San Francisco 49ers offensive lineman Anthony Davis has once again retired from the NFL.

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 on Sept. 15, and the team announced his retirement on Monday.

“I just want my time and mind intact, when you lose em both, you can’t buy em back,” he wrote on his Twitter account .

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 2011-13.