The Panthers have made several recent changes to their forwards. Vanek, 33 and an unrestricted free agent, was acquired by Florida in a trade from the Detroit Red Wings on March 1. He had 48 points (17 goals, 31 assists) in 68 games last season.
Last season was the final of a three-year, $19.5 million contract Vanek signed with the Minnesota Wild on the first day of free agency in 2014.
The Panthers bought out the contract of forward Jussi Jokinen on Saturday and signed center Micheal Haley and right wing Evgeni Dadonov.
Dadonov, 28, was the No. 71 pick in the 2007 NHL Draft by the Panthers and played 55 games for them between 2009 and 2012 before going to the Kontinental Hockey League.
Markov, 38, became a UFA at the end of his three-year, $17.25 million contract with the Canadiens. He had 36 points (six goals, 30 assists) in 62 games last season. After signing Karl Alzner and Joe Morrow on Saturday, the Canadiens had seven defensemen under contract for this season, including Shea Weber, Jeff Petry, David Schlemko, Brandon Davidson and Jordie Benn.