You may recall that yesterday, Frederik Andersen played one period in a loss to the Florida Panthers, and then never returned.
After the game, several things were said by Sheldon Keefe, including this:
Sheldon Keefe says Frederik Andersen is feeling better, passed concussion protocol & hasn't been ruled out of tomorrow's practice
Didn't know which play the injury occurred on— Mark Masters (@markhmasters) February 4, 2020Which makes it seem like the Leafs were using an excess of caution in keeping Andersen out of the game. One could simply assume that Kaskisuo is on hand for the practice, which does require a formal callup.