Capitals spokesman Sergey Kocharov writes in an email to The Associated Press on Thursday that Ovechkin's foot was hurt during Game 6 of Washington's first-round playoff series against the New York Rangers.
Washington lost that game 1-0 Sunday, and then lost 5-0 Monday in Game 7.
Ovechkin, who led the NHL with 32 goals during the regular season, scored only once against the Rangers, in Game 1.
He played Thursday for Russia in an 8-3 loss to the United States in the world championships in Finland.
Ovechkin's injury was first reported by The Washington Post's website.