Jarkko Immonen and Sakari Salminen of the KHL's Torpedo Nizhny Novgorod were added to the Olympic roster.
The Finns' chances to earn a medal for a fourth time since 1998 -- when NHL players began participating in the Olympics -- took a hit when it lost Filppula and Koivu.
Filppula has 20 goals, the most by an NHL player from Finland this season.
Koivu ranks third among players from his country in the NHL with 35 points this season. His brother, Saku, previously removed himself for consideration to play in the Olympics for a fifth time because the 39-year-old forward said he's not in good enough shape.