Coach Dan Bylsma says the 2011-12 league MVP was hurt during his first shift in Sunday's 1-0 loss to St. Louis. Malkin played the rest of the game but did not practice Monday. The Penguins would not say which foot was injured.
Malkin is seventh in the league with 72 points despite missing 11 games for various reasons. He had been playing some of his best hockey of the season before the injury, with four goals in three games.
Brandon Sutter will replace Malkin's spot on the second line. Bylsma said Malkin does not require surgery and the team anticipates Malkin being ready when the playoffs start April 16.
Teammate Jussi Jokinen knows losing Malkin is a big hit for Pittsburgh.
"If you lose a player like him, it's a big problem for the team," he said. "We still need to find a way to win."
The Penguins maintain the second spot in the Eastern Conference, seven points behind the Bruins.
The Associated Press contributed to this report.