"He's heading for free agency," his agent, Todd Reynolds, told The Toronto Sun's Terry Koshan. "The Leafs are aware of that."
Toronto's financial situation is forcing the issue, Koshan adds.
Reynolds said in March that Clifford has enjoyed his time in Toronto and the winger would be interested in staying with the Leafs.
Toronto acquired the bruising forward from the Los Angeles Kings along with goaltender Jack Campbell during the 2019-20 season. The Leafs included a conditional 2021 third-round pick in the deal that would be upgraded to a second-rounder if Clifford re-signed with Toronto.
The 29-year-old appeared in 16 regular-season games with the Leafs, registering three points and 43 hits while providing a much-needed physical presence.
He's coming off a five-year deal that carried an average annual value of $1.6 million.