The Patriots have released the 29-year-old running back ahead of Saturday's 4 p.m. ET deadline for roster cuts, ESPN's Adam Schefter reported.
Miller signed with New England on Aug. 13 and was placed on the Physically Unable to Perform list as he recovers from an Aug. 2019 torn ACL.
The Patriots activated Miller off the PUP list on Aug. 31, but running backs coach Ivan Fears recently suggested the former Pro Bowler still wasn't in playing shape.
"I really expect Lamar to bounce back and be the guy he was," Fears said Wednesday. "But I’m sure that’s going to take a little time."
Miller won't be subject to waivers as a fully vested veteran, and if another team doesn't scoop him up, he could land back on the Patriots' practice squad.
New NFL rules in 2020 allow teams to carry up to six players with unlimited NFL experience on their practice squads, so it's possible Miller could return to New England's practice squad as he gets up to speed.