Sergio Castillo kicked a 51-year field goal on the final play of the game, and the Winnipeg Blue Bombers captured their fourth straight CFL West Division title with 28-27 win over the Montreal Alouettes on Saturday.

Trailing by two as time wound down in the fourth quarter, Blue Bombers kicker Castillo booted his fifth field goal of the game to clinch top spot in the West for Winnipeg (11-7) in front of a sold-out crowd at Percival Molson Stadium.

Blue Bombers quarterback Zach Collaros went 24-for 32, throwing for 331 yards and one touchdown.

Wide receiver Nic Demski finished with a touchdown on 90 yards, allowing him to surpass 1,000 yards for the second straight season.

Alouettes starting quarterback Cody Fajardo completed 16 of his 20 passes for 171 yards and one touchdown in just under three quarters of action. Backup quarterback Davis Alexander took over behind centre late in the third quarter, finishing 7-of-9 passing for 100 yards and one rushing touchdown.

Montreal (12-5-1) had already clinched top spot in the East Division, a feat they accomplished for the first time since 2012.

Montreal linebacker Tyrice Beverette had five tackles, giving him 103 on the season. In so doing, he became just the seventh Alouette to ever surpass 100 tackles in a single season. He also added his fifth sack in the contest.

Alexander opened the fourth quarter with a one-yard rushing touchdown. The play came after he completed a 39-yard pass to Tyjon Lindsey, making his season debut for the Alouettes.

The Alouettes also wasted no time getting on the scoreboard to start the third quarter. Fajardo connected with Cole Spieker for a 47-yard reception to give Montreal a 20-9 advantage. Two plays later, Walter Fletcher rushed three yards into the end zone, capping off a seven-play, 84-yard drive.

After missing a 49-yard field goal attempt earlier in the quarter, Castillo was successful from 25 yards out to open the scoring for Winnipeg just over 10 minutes into the opening frame.

Montreal responded with a Jose Maltos 45-yard field goal to knot the score with 90 seconds to go in the first quarter.

Montreal scored the first touchdown of the game on a two-yard pass from Fajardo to Charleston Rambo just over five minutes into the second quarter to give the Alouettes their first lead of the game. Rambo's fifth touchdown of the season was made possible thanks to a 30-yard run by Sean Thomas Erlington and a 26-yard reception by Kaion Julien-Grant earlier in the drive.

Castillo added a field goal from 53 yards out to trim Montreal's lead to one. However, Maltos would connect on a 34-yard field goal to give Montreal a 13-9 lead as time expired in the first half.

Winnipeg scored their first touchdown of the game late in the third quarter. Collaros led the Blue Bombers on a three-play, 81-yard drive, resulting in a nine-yard touchdown pass to Demski.

They would add another score midway through the fourth quarter, thanks to a two-yard rush by backup quarterback Terry Wilson. Winnipeg's ensuing two-point convert attempt failed, preserving the Alouettes' then 27-25 lead.