Stolarz stopped seven of eight shots in the first period before leaving the game.
Anthony Stolarz won't return to Thursday's game against the Anaheim Ducks.
The Maple Leafs announced the news shortly after Joseph Woll entered the crease to begin the second period. Toronto is calling it a lower-body injury for the 30-year-old goaltender.
Stolarz allowed one goal on eight shots during the one period of play against the Ducks. It's the second straight game the goaltender is playing after stopping 38 of 39 saves on Tuesday against the New Jersey Devils.
It's unknown what caused Stolarz to leave the game after the first period.
Stolarz has appeared in 16 games with the Maple Leafs this season, winning nine and posting a .928 save percentage in that span. He's already halfway to his career-high in games played, which was 28 with Anaheim in the 2021-22 season.
The goaltender joined Toronto on a two-year, $5 million contract on July 1 after winning the Stanley Cup with the Florida Panthers in June. His contract's annual average value is $2.5 million.
Toronto's emergency backup goaltender is Michael Nishi, a 31-year-old netminder who last played for the University of Toronto in 2017-18.
After the game, Maple Leafs head coach Craig Berube updated Stolarz' update but didn't provide much.
"We'll know more tomorrow, lower body right now," Berube said. "It is concerning for sure. I didn't see when it happened or anything in the game, but yeah. Well, hopefully we got good news out of it."