MONTREAL — The Calgary Stampeders refused to celebrate their first-round playoff bye after their worst offensive performance of the season.

The first-place Stampeders barely defeated the last-place Montreal Alouettes 12-6 on Monday as they came from behind to win in the fourth quarter.

The victory guaranteed Calgary top spot in the Western Conference and home-field advantage in the West Final but there was no celebrating in the dressing room after the game. The message was the same all around — the goal is to win the Grey Cup.

"We're not there yet," said quarterback Bo Levi Mitchell. "Nothing to celebrate yet. When we get there, we'll celebrate that."

"It feels good but we don't really hang our hat on winning the West," said running back Terry Williams, who scored the game's only touchdown. "The ultimate goal is to do what we really want to do."

Added Stamps coach Dave Dickenson: "No celebration from this group. The celebratory thing will be when we can try to win something. It wasn't like we did anything well today. Our defence carried us. We know we have to play better in order to get to where we want to get to."

The loss eliminated Montreal (3-12) from playoff contention and guaranteed the Hamilton Tiger-Cats a playoff berth and one home-field post-season game in the CFL East.

Calgary (12-2) hardly looked like the league's best team on Monday.

The visitors went three quarters without scoring a single point — the first time they have more than one scoreless quarter in the same game this year.

It was also the first game this season where Mitchell failed to throw a touchdown pass.

He completed 20-of-34 passes for 199 yards and three interceptions as Calgary extended its winning run to three games.

"A win is a win but offensively we don't see it that way," said Mitchell, who was sacked three times. "We feel like we lost today. Two points in the standings but we have some work to do.

"It starts with me. I threw some balls today that were not okay, not safe throws. I put guys in bad positions."

Montreal has now failed to make the playoffs for a franchise-record four consecutive seasons. The Alouettes have not made the post-season since 2014.

"We didn't get to where we needed to be this year to be able to continue our season in the playoffs," said quarterback Johnny Manziel, who's still looking for his first CFL victory. "It's a (expletive) feeling."

Manziel went 18 for 29 for 250 yards and an interception.

Montreal's defence also played one of its best games. Chris Ackie, Branden Dozier and Dominique Ellis all got interceptions to keep the Als in the game.

After a scoreless first quarter, Boris Bede put Montreal ahead 3-0 with his first field goal of the afternoon, from 44 yards out, at 12:17 of the second quarter. Bede added a 41-yarder right on the stroke of halftime as the Alouettes went up 6-0.

That score held until the first play of the fourth quarter.

Capping off a drive that started at Calgary's three-yard line, Williams punched the ball into the end zone from six yards out. The big play of the drive was a 39-yard pass from Mitchell to Juwan Brescacin, who led both teams with 78 receiving yards.

Rene Paredes increased the Stamps' lead to 10-6 with a 49-yard field goal with 8:37 remaining in the game.

A punt into the end zone with 1:55 left on the clock gave Calgary the 11-6 lead. A missed field goal by Paredes in the game's dying seconds put the Stamps ahead 12-6.

Calgary had not beaten Montreal at Percival Molson Stadium in five games, dating back to July 12, 2013.

"We put everything into this game against a tremendous team," said Alouettes coach Mike Sherman. "We had a chance to win against one of the best teams in the CFL. We're close, we're knocking on the door, we're just not there yet. We took a huge step today."

Notes: The Alouettes gave up six sacks. They've now allowed five or more sacks in each of their last five games.