Washington had won four of its previous five to move one game over .500 (14-13) entering the game.
Murray said the Capitals played so poorly that they never came close to carrying out his game plan.
"Montreal has a young blue-line defensive corps, and we wanted to take advantage of it with some strong forechecking," he said, "but we couldn't even get through the neutral zone. They played a patient 1-2-2 defense in the neutral zone, and we tried to beat two men at the blue line. It didn't happen."
Murray said he had no explanations for the Capitals' lack of intensity.
Possibly, Washington was lulled to sleep by Montreal's recent performances at the Capital Centre. The Canadiens were 2-12-4 in their past 18 games here before last night.
Washington showed excellent passing at times in the first period to take a 2-1 lead, but the Capitals' play dipped in the second period.
They made sloppy passes and got called for untimely penalties. A two-minute elbowing penalty against Alan May at 9 minutes, 34 seconds of the period set a power-play opportunity for the Canadiens that resulted in Montreal taking a 3-2 lead 55 seconds later on a goal by left wing Mark Pederson.
Washington came back to tie the game 3:53 into the third period on a goal by Michal Pivonka.
Pivonka skated into the Montreal zone on the right wing, and, near the top of the right circle, blasted a high slap shot past goalie J.C. Bergeron's glove into the top right corner.
However, the Canadiens came back with what proved to be the winning goal with 5:33 left in the game.
Montreal center Andrew Cassels gave the visitors the 4-3 lead when he took a pass from Denis Savard at the left circle and skated at Washington goalie Don Beaupre to score inside the right post.
Beaupre was playing his first game after being out for 12 games with a groin pull.
"Beaupre [21 saves] was OK in the goal, but we didn't play well in front of him," Murray said. "We gave them too many breakaways."
Capitals defender Kevin Hatcher, who scored one goal in the loss, said of the team's effort: "We should be disappointed. We played pretty hard in the first period. I think we just plain and simple made too many mistakes, and they scored."
Montreal 1 2 1 -- 4
Washington 2 0 1 --3
First period--1, Washington, Hatcher 10, (Pivonka, Tatarinov), 4:41 (pp). 2, Montreal, Chorske 5 (Lebeau), 15:54. 3, Washington, Hunter 6 (Druce, Joyce), 17:59. Penalties--Dufresne, Mon (holding), 4:32; Miller, Was (holding), 8:43; Skrudland, Mon (roughing), 19:31; Hunter, Was (roughing), 19:31; Odelein, Mon (high-sticking), 20:00.
Second period--4, Montreal, Lebeau 10, 2:26. 5, Montreal, DTC Pederson 5 (Desjardins, Schneider), 10:20 (pp). Penalties--May, Was (elbowing), 9:34; Odelein, Mon, major (fighting), 11:58; Kypreos, Was (fighting), 11:58; Joyce, Was (holding), 12:23.
Third period--6, Washington, Pivonka 9 (Tatarinov), :53. 7, Montreal, Cassels 3 (Savard, Keane), 14:27. Penalties--Keane, Mon (unsportsmanlike conduct), 14:27; May, Was (unsportsmanlike conduct), 14:27.
Shots on goal--Montreal 8-9-7--24. Washington 11-7-6--24. Power-play opportunities--Montreal 1 of 3; Washington 1 of 2. Goalies--Montreal, Bergeron, 2-2-0 (24 shots-21 saves). Washington, Beaupre, 2-4-0 (24-20). A--15,887. Referee--Don Koharski. Linesmen--Ray Scapinello, Gord Broseker.