Koivu had a goal and an assist despite playing with the flu and a heavy heart the day after one of his best friends in hockey, defenceman Craig Rivet, was traded to the San Jose Sharks. Still, Koivu, 32, is on fire with 11 points in his last five games. "I slept all day Sunday and I didn't feel my best (Monday)," Koivu said. "When you feel that way, you try to do a little less and I guess sometimes less is more."
Montreal (33-26-6) scored on three of its four power-play chances - by Michael Ryder, Koivu and Sheldon Souray - as they built a 5-2 lead over two periods. Tomas Plekanec and Mike Johnson also scored.
Montreal hung on after the Leafs rallied with goals by Jeremy Williams and Alex Steen early in the third.
Toronto was incensed when officials failed to see a high stick by Garth Murray on Leafs captain Mats Sundin with 1:31 left in the third. The non-call stood up after a huddle among the four on-ice officials.
The Canadiens' fourth win in five games vaulted them over the idle New York Islanders and Carolina Hurricanes into seventh in the Eastern Conference, although both those teams hold games in hand.
Bates Battaglia and Bryan McCabe also scored for 10th-place Toronto (30-25-9), which ended a three-game road trip. The injury-riddled Leafs lost in regulation time for only the fourth time in 15 games.
"I like the way we responded - a lot of teams would have packed it in," said Leafs coach Paul Maurice.
Koivu was clearly disappointed to see the veteran Rivet traded to San Jose for young defenceman Josh Gorges and a first-round draft pick. And he was puzzled over the message it sent to the team.
Canadiens management denied it was a selloff and said they are still trying to make the playoffs, but Koivu saw it as a trade for the future. And at his age, Koivu hasn't many years left to try to win a Stanley Cup.
"I want to be a winner now instead of in five years," he said. "I don't know if I'll be here in five years.
"Why they did it? You have to ask (GM) Bob Gainey. Craig was a big part of the room here. You have to have young guys, but you can't have too many. You need a mix of veterans and young players."
However sick or disappointed, it didn't affect Koivu's play.
Koivu tipped a pass to Ryder for a goal in the first, then followed the play to score on Chris Higgins' rebound in the second.
"It's never fun to see a friend go, but even when things happen that you don't like, you know a professional like Saku is going to go on the ice and give his best effort," said coach Guy Carbonneau.
Carbonneau probably spoke for all 30 NHL clubs when he added "the whole team will feel the pressure lift" after the 3 p.m. ET NHL trading deadline Tuesday.
Toronto outshot Montreal 36-24, including 14-5 in the third.
Souray's goal from the point at 12:24 of the second chased Leafs goalie Andrew Raycroft, who gave up five goals on 16 shots in his 24th consecutive start.
Jean-Sebastien Aubin took over and stopped all eight shots he faced.
"I felt great," said Raycroft. "Then all of a sudden, it's 5-2.
"I don't think I was horrible, but I just couldn't find a way to get in front of anything."
Souray's 16th power-play goal of the season left him two short of the NHL record for defencemen set in 1974-'75 by Denis Potvin and tied in 1998-'99 by Adrian Aucoin.
His 22 goals is the most by an NHL defenceman since Sergei Gonchar had 26 in 2000-2001.
On Tuesday night, the Leafs are at home to face Buffalo while Montreal travels to New York to play the Rangers.
Battaglia lifted John Pohl's pass over David Aebischer 4:10 into the game, but Plekanec got it back at 5:48 after some gritty work in the corner by Alex Kovalev, who returned after missing seven games with a sore elbow.
Ryder converted Koivu's pass at 14:12 for his fifth goal in five games and Johnson scored off a faceoff won by Radek Bonk at 19:10.
McCabe's long shot eluded Aebischer on a power play 1:32 into the second but Koivu answered at 10:02.
A Sundin pass went off Battaglia's leg to Williams, who scored into an open side of the net 1:02 into the third. Williams, called up Friday from Toronto's AHL club, also scored in his NHL debut last April 18 against Pittsburgh. The Regina native had two goals on his first three NHL shots.
Steen was on his off-wing when his high wrist shot beat Aebischer at 4:40 and set up an exciting third.
"In the third, we just wanted to get a lot of shots on Aebischer," said Steen. "I was just trying to use the defenceman as a screen and it went in.
"It was nice."
Notes - Defenceman Brendan Bell didn't dress for the Leaf s. . . Montreal's Sergei Samonsov didn't play, but Koivu did for Montreal. Both missed practice Sunday with the flu . . . With Steve Begin returning from a broken foot, Andrei Kostitsyn was returned to Hamilton of the AHL. Janne Niinimaa was a healthy scratch while newly acquired Josh Gorges will join the team Tuesday in New York.