Blair, 27, was considered a valuable part of the 49ers' then-deep defensive line rotation. He is scheduled to become an unrestricted free agent next week.
The defender posted a video on Instagram, showing himself running and on his way to recovery, four months after the injury occurred.
The 49ers made Blair a fifth-round selection out of Appalachian State in 2016. He has recorded 88 combined tackles, 13.5 sacks, and a forced fumble through his four NFL seasons.
San Francisco went on to lose other key components of the defensive line to season-ending injuries, including Damontre Moore (fractured arm), D.J. Jones (high-ankle sprain), and Jullian Taylor (ACL).