Markstrom is being considered day-to-day at this time.
It was not immediately clear when or how Markstrom sustained the injury. With the club's No. 1 sidelined, David Rittich will get the start against the Maple Leafs, with Artem Zagidulin — who's yet to appear in an NHL game — activated from the taxi squad to serve as Rittich's backup.
In his most recent game, Markstrom struggled, allowing five goals on 15 shots in what became a 7-1 loss to the Edmonton Oilers.
On the year, the Flames goalie has posted an 8-6-1 record, with a 2.87 goals-against average and a .909 save percentage.