TORONTO — Calgary Stampeders rookie head coach Dave Dickenson pressed all the right buttons during his team's remarkable CFL season.

He led Calgary to a CFL-best 15-2-1 mark, the 15 victories a single-season league record for a first-year head coach. He was the overwhelming choice as coach of the year in voting by the Football Reporters of Canada and his coaching peers.

But with the Grey Cup on the line Sunday, Dickenson left himself wide open to be second-guessed.

After trailing Ottawa 27-7 in the third quarter, Calgary had whittled the deficit to 33-30 late in regulation. And the CFL's most potent offence, anchored by league MVP Bo Levi Mitchell at quarterback and rushing leader Jerome Messam, was second-and-goal at the Redblacks' two-yard line.

Dickenson decided to go with his short-yardage team, replacing Mitchell with Canadian rookie Andrew Buckley and moving the six-foot-three, 254-pound Messam — the CFL's top Canadian this season — up front to provide blocking support. The move wasn't without logic as the six-foot, 203-pound Buckley had eight rushing TDs on the year and scored on a one-yard run earlier in the game.

This time, though, Abdul Kanneh tackled Buckley for a one-yard loss and Calgary had to settle for a field goal to force overtime. Game MVP Henry Burris opened the extra session with an 18-yard TD strike to Ernest Jackson before the Redblacks' defence clinched the improbable 39-33 win by forcing Calgary's offence to go three-and-out.

The burning question was why, with the game on the line, didn't Dickenson call on Messam, who'd scored 11 rushing TDs during the regular season. Also, it was Messam's six-yard run that put Calgary at the Ottawa two-yard line.

"Either or," he said. "I'm sure you guys thought that and it might be the right case. We didn't necessarily have a great running game anyway. I gave him the look there on first down and he did a nice job, so we easily could've done something like that. But second thoughts, I called the game I thought would be the best for our team."

Dickenson's decision was similar to the one head coach Pete Carroll made in Seattle's 28-24 Super Bowl loss to New England on Feb. 1, 2015. Trailing 28-24, Seahawks quarterback Russell Wilson tried passing for the go-ahead touchdown rather than hand off to Marshawn Lynch, who had run for 102 yards in the game.

The move backfired as Malcolm Butler's interception preserved New England's victory. But unlike Dickenson, Carroll didn't take the league MVP out of the game and replace him with a first-year quarterback.

"I was going to either throw the ball or work a play that we had dialed up," Dickenson said. "I regret that call.

"I felt very confident that even if we went to overtime, I thought we had the momentum so I felt OK with kicking the field goal."

Calgary played most of the contest without leading receiver Marquay McDaniel, who left in the first half with a shoulder injury following a 51-yard reception. On Monday, he couldn't hide his disappointment with the final outcome.

"Now I know how the Seahawks feel," McDaniel tweeted.

Mitchell finished 28-of-41 passing for 391 yards and two TDs but also threw three interceptions after having just eight in the regular season. Still, Mitchell felt he and Messam should have been given the opportunity to deliver the victory.

"Ball's got to be in my hands and (Messam's)," he said. "That's how I feel. But it's not wrong, for what he called it's a good call, it's something we've seen in film with evidence we thought would work. And they've got a solid D-line so it's not to say even if we would've handed off that he (Messam) would've got in but at that moment I thought the game was over."

On Monday, Messam tweeted: "Thank you for all the support but the game was bigger than one play. What's done is done and today is a new day #wellbeback."