The defenceman has been placed on injured reserve, according to the NHL roster page.
Tanev exited Saturday’s win over the Colorado Avalanche halfway through the first period with an upper-body injury.
The 36-year-old skated off in visible discomfort after a collision with Avalanche forward Artturi Lehkonen in front of the Maple Leafs’ net.
Tanev has one assist over Toronto’s first six games while averaging 16:51 of ice time per contest.
The veteran blue liner was limited to just 11 games last season by multiple injuries and underwent season-ending core muscle surgery in March.
The Maple Leafs recalled Marshall Rifai from the Toronto Marlies in a corresponding move. He’s been held pointless through three games in the AHL this season.
Rifai has just three games of NHL experience, all with the Maple Leafs.