Updated

Nathan Beaulieu's power-play goal at 8:00 of the third period proved to be the game-winner as the Saint John Sea Dogs edged the Mississauga St. Michael's Majors 4-3 on Friday in the opening game of the MasterCard Memorial Cup.

Beaulieu's goal on a play that appeared to be offside gave the Quebec Major Junior Hockey League champions a 4-2 advantage. Mississauga, the host team, made it 4-3 when Casey Cizikas scored with the man advantage just 33 seconds later, delighting the Hershey Centre crowd of 5,429.

Beaulieu said he didn't know if the play leading up to his goal should've been blown dead.

"I couldn't tell you," Beaulieu said. "After I just heard a lot of boos and stuff."

Mississauga coach Dave Cameron felt there was no question that the play should have been called.

"Yes," he said when asked if the offside call was missed. "Mistakes happen. They made a mistake."

But Cameron also said Mississauga's lack of discipline played a role in the loss. Saint John finished the game 3-for-8 on the power play. The Majors were 2-of-7 with the man advantage.

"We lost our composure," Cameron said. "No doubt about it."

The Sea Dogs came into this event as the top-ranked junior squad, two spots ahead of a Majors team playing its first game since a 3-2 overtime loss to the Owen Sound Attack at the Hershey Centre on Sunday in the Ontario Hockey League final.

"We weren't so much the better team but more we got a couple of bounces," Beaulieu said. "We didn't play our best game at all and I give full credit to them for working so hard.

"Holding that one-goal lead wasn't easy and I thought we did that real well so credit to our guys. Our special teams were really good and were our biggest keys to the win."

Tomas Jurco, Michael Kirkpatrick and Jonathan Huberdeau had the other goals for the Sea Dogs, who tied a QMJHL record with 58 wins this season and were 10-0 on the road during their playoff run.

Cizikas scored twice and Devante Smith-Pelly also connected for Mississauga, the OHL's top defensive team during the season with just 170 goals allowed in 68 games

Saint John grabbed a quick lead when Jurco beat goaltender J.P. Anderson with a backhander on a partial breakaway 1:44 into the game.

Cizikas tied it at 7:07 and Smith-Pelly's power-play goal at 13:55 put the Majors ahead. But Saint John countered with a power-play goal of its own from Huberdeau late in the period to make it 2-2.

Kirkpatrick got Saint John's second power-play goal at 6:58 of the second to put the Sea Dogs ahead 3-2. Cizikas nearly tied it early in the third period, but he hit the post with a wrist shot during a 5-on-3 power play.

The tournament continues Saturday when Owen Sound takes on the Western Hockey League-champion Kootenay Ice in the first game for both teams (7 p.m. ET, NHL Network-US). Kootenay finished the regular season fourth in the Eastern Conference but posted a 16-3 playoff record en route to capturing its third WHL crown.

Owen Sound finished eighth in the CHL's top-10 ranking and posted a 16-6 playoff record in earning the first OHL title in its 22-year history after relocating from Guelph, Ont.

Material from wire services was used in this report