REGINA — Justin Medlock kicked a 28-yard field goal in overtime to give the Winnipeg Blue Bombers a 43-40 walkoff victory, spoiling the Saskatchewan Roughriders' home opener at new Mosaic Stadium on Saturday.

Roughriders kicker Tyler Crapigna saw his 33-yard field goal slam into the upright, which kept the score tied at 40-40.

That missed attempt was Crapigna's second crucial miss in consecutive weeks. His potential game-winning boot a week earlier in Montreal sailed wide and allowed the Alouettes to rally for a victory.

Winnipeg and Saskatchewan traded field goals with their first possessions of overtime.

Kevin Glenn rallied the Roughriders from a 14-point deficit in the fourth quarter to set the stage for overtime.

The teams were tied 37-37 at the end of regulation.

Trailing 37-23 early in the fourth quarter, Glenn hooked up with Nic Demski (27 yards) and Naaman Roosevelt (15 yards). The second touchdown evened the score at 37-37.

After a sloppy third quarter from the Roughriders defence, the unit held its ground in the fourth quarter to allow the offence to mount a rally.

Winnipeg quarterback Matt Nichols threw for four touchdowns, two to Weston Dressler, as the Blue Bombers staged a rally of their own in the third quarter.

Dressler's two touchdowns — one for 87 yards and the other for nine yards — came 35 seconds apart in the opening minutes after halftime.

Winnipeg trailed 17-13 at the half, but erupted for 21 points in the quarter to take a 34-23 lead.

Dressler, a former Roughriders star, was left wide open on his first touchdown reception.

Greg Morris fumbled the ensuing kickoff and the Blue Bombers recovered at the Riders' nine-yard line. On the next play from scrimmage, Nichols found Dressler wide open again for a nine-yard touchdown that gave the visitors a 27-17 lead.

After a field goal from Crapigna, the Blue Bombers responded with their third touchdown, a 35-yard strike from Nichols to L'Damien Washington.

Saskatchewan built a 17-3 lead late in the first half thanks to a pair of touchdown passes from Glenn to Caleb Holley (18 yards) and Bakari Grant (10 yards). Crapigna opened the scoring for the Riders with a 48-yard field goal.

A 31-yard touchdown strike to Darvin Adams, followed by a Sam Hurl interception seemed to spark the Blue Bombers late in the half.

Medlock kicked a 17-yard field goal to close out the first half, with Winnipeg trailing 17-13.

In Week 3, Winnipeg will host the Calgary Stampeders, while the Riders will welcome the Hamilton Tiger-Cats to Regina.