Miller sustained a fractured scapula in Sunday’s win over the Tampa Bay Buccaneers. Tukuafu played for the 49ers last season on both sides of the ball, getting extensive work as a short-yardage fullback. But in the preseason, he did all of his work on the defensive side.
He made the opening-week roster, but was waived on Sept. 10 with a knee injury. His injury settlement allowed him to rejoin the team this season.
Anthony Dixon is the likely starter at fullback with Miller out.
Tukuafu played in 13 games last season and made five tackles. He was an undrafted free agent out of Oregon who was originally signed by the Seattle Seahawks before coming to the 49ers.