"They're a good team and they came hard and forced us into bad spots," Canadiens defenseman Hal Gill said.
"I think we did some good things but we have to do a lot more of the better things, a lot more winning battles, a lot more support. It's a simple game that they play but it's a deliberate game and it's a hard game, and we didn't match that the way we should have."
Canadiens captain Brian Gionta left the game in the third. He suffered an upper-body injury and did not return.
Price lost his starting job in 2009-10 to Halak, who led Montreal to playoff upsets that spring over Washington and Pittsburgh, the No. 1 seed and defending Stanley Cup champions, respectively.
The Canadiens elected to move forward with Price, the fifth overall pick in the 2005 draft, and Halak was dealt to St. Louis in return for Lars Eller and Ian Schultz.
The two goalies faced each other for the first time in St. Louis on March 10. Halak made 27 saves in the Blues' 4-1 win.
Arnott opened the scoring midway through the second. The 37-year-old center scored for a second straight game 9:51 into the middle period when he drove in to pick up Ryan Reaves' rebound and reached around a sprawled Price for his 10th goal.
St. Louis took advantage of another rebound to go up by two at 14:58. Backes fired his 14th goal past Price, who stopped Stewart's initial shot from in close.
Stewart teamed up with Backes to score the Blues' third goal 12:56 into the third.
Halak's previous game at the Bell Centre was a 3-0 loss to Philadelphia on May 22, 2010, in the fourth game of the Eastern Conference finals. ... Canadiens C Petteri Nokelainen was left out of the lineup for a second game in a row.
Copyright by STATS LLC and The Associated Press
MONTREAL, CANADA - JANUARY 10: A young fan shows his support to former Montrealer Jaroslav Halak #41 for his first...