The Toronto Maple Leafs have placed defenceman Chris Tanev on injured reserve retroactive to October 21 with an upper-body injury. Dakota Mermis has been called up from the AHL’s Toronto Marlies.

Tanev suffered the injury during Tuesday’s loss to the New Jersey Devils, and was ruled out of the game during the third period, after colliding with Devils forward Dawson Mercer. He skated to the locker room directly and did not return to the game.

As a result of the IR designation retroactive to October 21, Tanev will not eligible for another seven days, and his earliest possible return date is October 29 against the Columbus Blue Jackets.

The 35-year-old was previously deemed questionable for Friday and Saturday’s games against the Buffalo Sabres.

“I’m not going to lie with you, when he stays down it’s definitely scary because I have never played with a guy as tough as Chris Tanev,” Maple Leafs forward Max Domi said Wednesday via TSN’s Mark Masters. “So, it’s not a good feeling, as a group, when you see a guy like that go down, but he seems to be doing well and tough as nails.”

Tanev is the Maple Leafs’ best defensive defenceman, and one of the NHL’s premier shot-blockers, so it’s a difficult loss for the Maple Leafs to manage through the opening month of the season. He has recorded one assist through seven games this season.

It’s widely expected that Philippe Myers will slot into the lineup to replace Tanev, although Mermis and Henry Thrun are potential options for head coach Craig Berube to consider ahead of this weekend’s home-and-home slate.

Mermis appeared in three games for the Maple Leafs last season, recording one assist. He was called up several times, and primarily spent the year with the Marlies, where he recorded seven assists in 32 AHL contests.