Rask sustained the injury in the second period of the Bruins' 3-2 loss to the New York Islanders.
Rask has played in 23 games this season and is 11-8-3 with a 2.05 goals against average and a .929 save percentage. Three of Rask's wins were shutouts.
Without Rask available that means that starting goalie Tim Thomas won't be able to get much rest down the final stretch of the regular season. Michael Hutchinson has already been called up from the AHL Providence Bruins. Hutchinson has 6 wins and 11 losses for Providence this season. However, he does have a 2.62 GAA and a .920 save percentage.