After playing four extra periods in the first two games, the Bruins made an early night of it with second-period goals by Daniel Paille and Patrice Bergeron to win 2-0 and take a 2-1 lead in the Stanley Cup finals.
"A win is a win. We'll take a win any day," said Rask, who stopped 28 shots for his third shutout of the 2013 playoffs. "We'll take a regulation win, for sure."
Corey Crawford made 33 saves for the Blackhawks.
Game 4 is Wednesday night in Boston before the matchup of Original Six franchises returns to Chicago for a fifth game. The teams split the first two games there, with the Blackhawks winning Game 1 in triple-overtime and the Bruins stealing home-ice advantage on Paille's goal in the first OT of the second game.
But this time the intrigue came before the opening faceoff instead of after the end of regulation.
Bruins defenseman Zdeno Chara and Chicago forward Marian Hossa both left the ice after warmups. But while Chara needed just some stitches after his collision with teammate Milan Lucic, Hossa was a late scratch with an unspecified injury.
"I was as surprised as anybody else," Bruins coach Claude Julien said. "I can definitely tell you they lost a pretty important player on their roster, but that doesn't mean we change our game. I think it's important we stick with what we believe in."
Julien said Chara slipped and "had a little gash over his eye."
"Nothing serious," Julien said of his captain and No. 1 defenseman, who still managed to lead the team in ice time.