Head athletic therapist Paul Ayotte and members of the sports science team watched as Andersen went through his paces with goalie coach Steve Briere. At one point, Andersen went over to the bench and stretched his right arm above his head while Ayotte rubbed his shoulder.
This was a little more than 36 hours after Andersen left Saturday’s game in Buffalo with an undisclosed upper-body injury.
His status for Tuesday’s game against Florida is unclear.
Andersen missed September’s World Cup and the start of Leafs training camp with a shoulder injury suffered in Olympic qualifying with Denmark. He also has a concussion history, having suffered one while playing for the Anaheim Ducks last April.
The Dane was involved in two collisions with Sabres players during a busy first period on Saturday before being replaced by backup Curtis McElhinney during the intermission.
McElhinney and Garret Sparks, who is third in the American Hockey League with a .927 save percentage and was recalled on Monday morning, took the ice after Andersen left.
The Leafs have relied heavily on their No. 1 goalie this season – using Andersen in 61 of 74 games so far.
The team has eight games left on its regular-season schedule and is sitting third in the Atlantic Division.