Johnsson had a CT scan Thursday, and the Maple Leafs said he will be reassessed by the Toronto medical staff after the Christmas break.
He has 16 points (six goals, 10 assists) in 30 games this season. He had 43 points (20 goals, 23 assists) in 73 games last season, and four points (one goal, three assists) in seven Stanley Cup Playoff games.
The Maple Leafs recalled defenseman Martin Marincin and forwards Nic Petan and Pontus Aberg from Toronto of the American Hockey League on Friday. They begin a four-game road trip against the St. Louis Blues on Saturday (7 p.m. ET; NHLN, CBC, SN, SN360, CITY, TVAS, FS-MW, NHL.TV).