Howard dressed as the backup to Jonas Gustavsson in a 5-0 loss to the Philadelphia Flyers on Tuesday. He hasn't played since Jan. 20, when he left a game against the St. Louis Blues in the second period due to discomfort in his knee.
Zetterberg, who has two goals and six assists during a four-game point streak, hasn't played since Jan. 24 against the Montreal Canadiens due to a sore back. He has 16 goals and 44 points in 40 games this season.
Daniel Cleary will come out of the lineup to make room for Zetterberg.
The Capitals, meanwhile, don't expect to know until game time whether defenseman Mike Green will be in the lineup.