Tom Anselmi, president of Maple Leaf Sports and Entertainment, which owns the team, told reporters Burke was being reassigned as a special adviser to the team after four years at the helm, during which the Leafs failed to make the playoffs, the Canadian Broadcasting Corp. reported.
"We've decided to make a leadership change and move in a different direction for the general manager role," Anselmi said. "This was a decision that the board and myself collectively made. It's the product of a conversation that has been going on for some time."
The firing came as something of a surprise because Burke, 57, had two years remaining on his contract. Like Nonis, he had previously served as general manager with Vancouver, as well as with Anaheim and Hartford.
The team went 128-135-42 under his reign.
Nonis becomes the 14th GM in Maple Leafs' history. He confirmed Randy Carlyle would remain the Maple Leafs' head coach, the CBC reported.