Montreal was eliminated from CONCACAF Champions League competition despite a 2-0 win over CD Heredia on Tuesday night.
The Impact, who won the Amway Canadian Championship, needed to score early and often to keep their slim hopes of advancing past the group stage alive.
Montreal, which had lost its last two Major League Soccer games at home, managed the first part when Daniele Paponi scored just four minutes in to the delight of the enthusiastic Saputo Stadium crowd of 13,703.
Andrew Wenger made it 2-0 in the 54th minute but the Impact needed to win by at least six goals to avoid being knocked out of their second Champions League competition, and their first since 2008.
"It is bittersweet," said Montreal goalkeeper Evan Bush, who played every minute of the Impact's games in ACC and CONCACAF Champions League competition. "After the game you can't really celebrate it. You're happy you won and psychologically it's good to break a three-game losing streak over the two competitions, but at the same time we knew what we had to do and the goal was 6-0, not 2-0."
CD Heredia would have clinched the three-team Group 5 with a draw or a win after 1-0 victories in both of their home games against Montreal and the San Jose Earthquakes.
"The Impact are a very fast team so we had to adjust our strategy," CD Heredia coach Juan Carlos Elias said in Spanish through an interpreter. "Our tactics weren't as good as theirs were. They were just faster on the ball. They were just faster in every situation than we were."
The Guatemalan side can still move through to the championship round with a point in the final group stage game next month in San Jose.
An Earthquakes win on Oct. 23 would bring about a three-way tie and San Jose, which beat Montreal 3-0 last Tuesday, would advance by virtue of the best goal-differential.
The Impact are third in the MLS Eastern Conference with 45 points in 28 games. They play in Chicago on Saturday and are on the road for four of their six remaining regular season games.
"It was very important to finish like this for the morale," Montreal coach Marco Schallibaum said. "I think the team was very well prepared and they had a good mentality tonight. Of course they could have scored more goals, it was only 2-0, but I think the way they played tonight, I think that's the way we want to go with together because the guys gave everything for the club and the result. We won the game, but that was not enough, but I think the base was very solid."
Defender Hassoun Camara and midfielder Felipe were the only two regulars in Montreal's starting 11, which included three Quebecers on the back line _ defenders Karl Ouimette, Maxim Tissot and Wandrille Lefevre.
"It's incredible the experience you get by just being on the field and playing at this level," Ouimette said.
Marco Di Vaio entered in the 57th minute and quickly made his presence felt. The 37-year-old Italian striker dove to head Wenger's centring pass, forcing goalkeeper Jose Calderon to dive to his right to deny Di Vaio's sparkling attempt.
Impact forward Justin Mapp replaced Andrea Pisanu 66 minutes in.
Both Di Vaio and Mapp put drives off the post as the Impact pressed for more offence without success.
"We came out there and right from the get-go we attacked," Wenger said. "It was a very open game and we showed some quality, unfortunately we weren't as decisive in five more moments and that would have _ obviously we'd be celebrating, everything would be perfect now, but we put in a good showing."
Paponi was shown a yellow card 78 minutes in by Jamaican referee Courtney Campbell, who judged that the Montreal forward dove when he was met with a challenge from behind as he approached the 18-yard box.
"I was sure it was a foul and when the referee came to me I thought it was a joke," Paponi said in Italian through an interpreter. "When I got the card I was in disbelief. The referee didn't say anything but even the defender on the other team admitted to me that it was a foul."
The crowd's enthusiasm had long soured by that point after starting off the game with a bang.
A small fireworks rocket came shooting out of the Ultras section behind CD Heredia's goal and exploded over the field less than two minutes in.
Smoke from the stands was swirling around the goalmouth when Paponi scored four minutes in, putting away a rebound of Felipe's shot.
CD Heredia came close to evening the score in the 26th minute but Charles Cordoba's shot while prone in a goalmouth scramble went off Impact defender Karl Ouimette's face and stayed out.
Paponi had an opportunity in stoppage time at the end of the first half but Calderon came out to challenge and clear the ball from harm.
Wenger added Montreal's second goal when he was sent in alone on a through ball from Tissot.