The Stamps scored 16 points after halftime against the B.C. Lions on Saturday night, but it wasn't enough as Calgary suffered a 27-22 loss.
A win would have tied Calgary with the Lions for the division lead.
Despite the fact that B.C. was without its two star receivers in Geroy Simon and Arland Bruce III, Calgary's defence was unable to contain the Lions quarterback Travis Lulay and his deep receiving core.
Calgary linebacker Juwan Simpson was unhappy with the way his team started the game.
"If we played the first half like we did the second half, I think we'd come out with a win," said Simpson.
Stampeders quarterback Kevin Glenn threw for 141 yards and one touchdown in the second half after putting up 101 yards and no touchdowns in the first half. He also threw two interceptions on the night.
Calgary head coach John Hufnagel thought Glenn could have been better.
"There were some throws I thought he could have made," he said. "On the second interception he just didn't get enough on the ball."
Lulay, meanwhile, put up 268 passing yards with two touchdowns and no interceptions.
Calgary squandered a 61-yard effort by CFL rushing leading John Cornish. Last time the two teams met on July 28, Cornish managed a negative one yard performance in a 34-8 loss. Cornish also put up 32 receiving yards for 93 total yards on the night.
Meanwhile, fellow Canadian Andrew Harris managed 73 yards on the ground and 52 yards in the air for a total of 125 yards. Harris is now 85 yards short of reaching the 1,000-yard mark. If he manages it in the Lions' remaining four games, it will be only the third time in history two Canadians have accomplished the feat in the same season. Cornish has 1,188 yards rushing so far in 2012.
Simpson said the Stampeders will need to look ahead after the tight loss.
"That's behind us now. We've just gotta get in the film room, take some directions in, and get ready for Winnipeg."
The two teams will face each other again in their penultimate games of the season on Oct. 26.