Calgary is double-digits better than Winnipeg especially when playing at home. 
The oddsmaker opened the Stampeders a little light because Calgary was upset by BC last Saturday, 20-18. That was the Stampeders' first season-opening loss since 2011 and should prove a wake-up call especially after blowing an 11-point second half lead. 
The last time Calgary lost two games in a row in a season was early in 2012. That's the longest streak in Canadian pro football history. Calgary is 21-6 ATS following a loss.  
Winnipeg is a bottom-three team that looked bad in losing at home to Montreal to start the season last week. Drew Willy was sacked five times and didn't look good. The Blue Bombers are averaging just 17.2 points during their last four games. So their poor offensive performance wasn't a surprise. 

These teams are familiar with each other having just recently played a preseason game in which there were fewer than 50 points scored. 
Winnipeg upgraded its defense during the preseason particularly in the defensive line and at linebacker. 
Montreal has a strong defense led by defensive end John Bowman, who led the CFL with 19 sacks last year. The Alouettes have weapons, but quarterback Kevin Glenn is 37 and doesn't have a solid backup. The Alouettes also have a young, untested offensive line that will be missing star tackle Josh Bourke and injured center Luc Brodeur-Jourdain. Those are two key missing pieces. 
There also are a number of strong trends that point to an under in this matchup. Montreal has gone below the total in 18 of its last 21 games played in June. The Alouettes also are 16-6 to the under in their past 22 away contests. Winnipeg is 6-1-1 to the under in its last eight home games and only has gone above the total just four times during its last 16 overall games.