The Maple Leafs assigned Mrázek to the AHL club on Friday on an LTIR conditioning loan.
Mrázek injured his groin in the second game of the season against the Ottawa Senators before taking two weeks off to rehab. He returned for the Oct. 30 game against the Detroit Red Wings, but felt a recurrence of the injury.
The 29-year-old has been out ever since, but joined the Leafs on their recent road trip and sits on the cusp of seeing game action.
Mrázek was a full practice participant for the Leafs on Tuesday for the first time since reaggravating his groin injury.
While Mrázek has been out, the Leafs relied largely on No. 1 Jack Campbell and have gone 16-6-1 throughout November, finishing an NHL-best 12-2-0 to set a franchise record for victories in a calendar month.
During Toronto's November surge, Campbell was 9-2-0 with .959 save percentage and rookie third-stringer Joseph Woll went 3-0-0 with a .939 save percentage in his first three NHL starts.
--with files from The Canadian Press