Mrazek was placed on injured reserve retroactive to Nov. 4 after re-aggravating the groin injury he suffered on Oct. 14 in Ottawa.
The 29-year-old is 1-1 this season with a 4.20 GAA and a .877 save percentage. He was signed to a three-year, $11.4-million contract as a free agent this past off-season and expected to compete with Jack Campbell for starts in a tandem.
The Leafs recalled goaltender Joseph Woll to be Campbell's backup against the Boston Bruins Saturday. They also promoted forwards Joey Anderson and Kirill Semyonov from the AHL's Toronto Marlies on Sunday.