The victim of a woeful first-half performance, the Impact were beaten 1-0 by a Toronto team that started the day 23 points behind its Canadian rival.
Robert Earnshaw scored his team-leading eighth goal of the season in the 16th minute for Toronto (6-17-11), which could have led by three after the first 45 minutes of the regular-season finale for both clubs. Earnshaw celebrated with his trademark somersault, followed by a matador salute.
Once a force in the East, the Impact have collected four of a possible 24 points available over their last eight games (1-6-1).
"The first half, we weren't very good," said Impact coach Marco Schallibaum. "A lot of mistakes, a lot of tension. There were errors.
"The second half was better. Not much better, but better. There were also chances to score, maybe (make it) 1-1. But it was not good enough to win this game today. And that's a pity"
Just how much of a pity will become clear Sunday.
Montreal (14-13-7, 49 points) will be out if Houston beats D.C. United, New England defeats Columbus and Chicago beats or ties New York. It could be worse, but the Impact could have rendered Sunday's results meaningless had they shown up Saturday.
Asked if he is confident he will get the results he needs, Schallibaum replied: "That's not up to us. we must now wait for the last game. And then we make the calculation."
With just Toronto, D.C. United and the Columbus Crew eliminated from playoff contention and New York and Sporting Kansas City already in, it made for a complicated final weekend in the East with Montreal, Chicago, New England, Houston and Philadelphia vying for the final three playoff berths.
Philadelphia was ousted after losing 2-1 to Sporting Kansas City earlier in the day. The Union had needed a win and help from other teams.
Chicago (49 points), Houston (48) and New England (48) all get their chance Sunday.
The Impact went into the weekend in the best position, tied with Chicago on points but well ahead in the next tiebreaker (goals for).
There was little on the line for Toronto other than pride — and the chance to pick up a sixth win, one more than last season when the team went 5-21-8.
For rookie manager Ryan Nelsen, it was a performance that showed a taste of things to come after a bumpy season.
"This team, from the first day I came in, we were in a black hole — we were in a monster black hole," he said. "So big I didn't think we were going to be able to get out of it in just a year. I thought it would take two or three, to tell you the truth."
Nelsen said he was prepared to take the criticism this season while building for the future.
"All I wanted to do this year is produce exciting young players, develop them. Get away our (salary cap) debut as a club, which we've done. And now we've laid a nice foundation where we can move forward. Which I don't think we've really had in the past."
Nelsen said there is still a huge job ahead. But he likes what he sees.
"We've evolved as a young team, we've matured," he said.
It was a "win and you're in" game for Montreal but there was little sense of urgency from the visitors despite the cheers of a phalanx of Impact supporters squeezed in the corner of the east stand of BMO Field.
After a sluggish start by both teams, Toronto began to take control. At times Toronto players were queuing up to take a shot.
Outshot 10-5 in the first half (5-0 in shots on target), the Impact managed 10 shots in the second but only three were on target.
Montreal made changes in the second half and began to finally test the Toronto defence. The Impact outshot Toronto 10-6 in the second half but only put three shots on target to Toronto's two.
When Montreal did find its aim, Toronto goalkeeper Joe Bendik was equal to the task.
He stopped Davey Arnaud at point-blank range in the 53rd minute. And he robbed Andres Romero in the 88th minute.
Montreal misfired the rest of the time.
A 62nd-minute goal by Marco Di Vaio was called off due to apparent handball. Three minutes later, substitute Andrea Pisanu headed just wide. Andrew Wenger shot wide from in front of the net in the 72nd minute.
Toronto's goal had a hint of luck about it but was nevertheless deserved as the home side began to launch attacks with rookie Canadian midfielders Jonathan Osorio and Kyle Bekker pulling the strings while dominating Montreal's Hernan Bernadello and Felipe.
Toronto striker Bright Dike's physical presence also disrupted the Montreal defence. The bull-like forward set the table for the Earnshaw goal.
After Dike tormented a pair of Montreal defenders, the ball squibbed free to Osorio whose right-footed shot was redirected in by Earnshaw, catching goalie Troy Perkins going the wrong way.
Earnshaw had a fine chance in the 33rd when he and Dike broke in side-by-side down the middle during a defensive breakdown. Perkins saved the day, making a fine point-blank save.
The Impact goalie was forced to make a fingertip save off Osorio seconds later as Montreal's defence — missing the injured Alessandro Nesta — continued to crumble.
Bekker hit the crossbar in the 38th minute from outside the penalty box. Perkins then had to tip an Earnshaw shot over the bar in the 43rd minute.
Toronto came close early in the second half with a header from skipper Steven Caldwell deflecting off the bar. Caldwell had another chance in the 82nd minute off a corner but a Montreal defender made a goal-line clearance.
"The only thing that disappointed me was we didn't get that second goal," said Nelsen.
Toronto was coming off a 1-0 loss in Chicago, a defeat that stretched its league road scoring drought to six hours 45 minutes. Toronto has failed to make the playoffs since entering the league in 2007.
While it has been another long season for TFC supporters, there may be light at the end of the tunnel. Nelsen will be less constrained by the salary cap next season and the team says it is willing to spend big on marquee strikers in the January transfer window.
The club can also point to a corps of talented youngsters. Saturday's starting 11 featured seven players 25 or younger.
A black cat ran across the north goal prior to the game. Perhaps coincidentally that goal needed some repair work prior to kickoff, resulting in a kickoff delay of about five minutes.
A tuque giveaway was doubtless appreciated by the fans on a chilly overcast, seven-degree afternoon at the Toronto lakefront. The sun eventually came out but it was still a raw day for the announced crowd of 13,211.