Matthews, who leads the league with 59 goals, was absent from morning skate due to illness and has been ruled a game-time decision for his club's third and final meeting against the playoff-hunting Washington Capitals.
Matthews has missed only one game this season, due to a flu bug on Dec. 16, and is on pace for 68 goals. Ovechkin peaked with 65 in 2007-08.
Coach Sheldon Keefe said Matthews is dealing with something "a little different" than the flu bug that has trickled through the Leafs' dressing room this winter.
"Hopeful that it's more manageable that he could be available tonight," Keefe said, "but see how the extra rest today benefits him."