SAINT JOHN, New Brunswick — A hot goaltender and an ill-timed penalty have put the Lewiston Maineiacs in a precarious position.

Mathieu Corbeil, though an NHL draft pick, played in only one playoff game prior to his relief appearance late in Game 1 on Friday. He made Saint John coach Gerard Gallant’s choice to start him Saturday appear brilliant, stopping 24 of the 25 shots he saw while the vaunted Sea Dogs’ offense took care of business at the other end with four goals — including three on the power play — as Saint John defeated the Lewiston Maineiacs 4-1 to take a commanding 2-0 series lead in the Quebec Major Junior Hockey League semifinals.

“(Corbeil) played a game against Cape Breton and he had a shutout,” Saint John coach Gerard Gallant said. “Then (Friday) night he made three or four great saves to get the win for us when he came in. I’ve been rotating the goalies all season long, and there was no second-guessing. It was an easy decision to go with him (Saturday) night.”

The Sea Dogs had plenty of early chances, but a five-minute major and game misconduct officials assessed Lewiston defender Olivier Dame-Malka in the second period gave the Saint John offense the spark it needed. Stanislav Galiev, Kevin Gagne and Jonathan Huberdeau all scored during the five-minute, non-releasable man advantage to push the lead to an insurmountable four goals.

“You can’t be in the box for 20 minutes against this team, you’re not going to win the game,” Maineiacs’ coach J.F. Houle said. “Then we ran out of juice. We had nothing. We were flat. We just didn’t have the fire and the heart that we had last night. We just ran out of energy.”

“The first two periods were outstanding,” Gallant said. “We didn’t give them odd-man rushes. We slowed their transition game down and I thought our forecheck was a lot better.”

The outburst also prompted Houle to pull 20-year-old keeper Nick Champion in favor of 17-year-old Russian rookie Andrey Makarov, giving the youngster his first sniff of playoff hockey.

Corbeil, meanwhile, has allowed just this one goal in the playoffs, stopping all 13 shots he saw in Game 1 to go along with a shutout against Cape Breton. His shutout streak reached 121 minutes and 43 seconds before a Lewiston goal in the third period on Saturday.

The Maineiacs again got off to a sluggish start Saturday, and again the Sea Dogs cashed in. Less than three minutes into the game, Michael Kirkpatrick pivoted in the low left circle and fired the puck through a minor screen and beat Champion for the first goal of the contest.

Buoyed by three consecutive power plays — including 55 seconds of 5-on-3 play — Saint John piled on the shots. Champion was equal to the task, stopping a handful of Sea Dogs down low and keeping the Maineiacs within striking distance. One stop in particular, on Galiev alone in front with his left pad, left the crowd stunned.

On the other side, Corbeil was rarely tested, though he made one good stop early on a Kirill Kabanov-Etienne Brodeur 2-on-1 break.

“They were the better team in the first period, and pretty much the whole game I thought they were the better team,” Houle said. “You can’t be undisciplined against this team, it’s going to cost you. And it cost us.”

The Maineiacs did test the Saint John keeper early in the second. Antoine Houde-Caron produced a turnover behind the Sea Dogs’ net and fed Cameron Critchlow alone in front. Critchlow directed his one-timer to the left post, and Corbeil denied the Lewiston captain with the right pad.

After the outburst in the second, the Sea Dogs quieted down on offense, and Lewiston began to generate a few more chances. The Maineiacs finally solved the big keeper at 9:54 of the third frame when Kabanov backhanded his own rebound past Corbeil at the left post.

“The third period, it was 4-0 and we stopped playing,” Gallant said.

The teams will take two days off and resume their best-of-seven semifinal in Lewiston on Tuesday in Game 3. Game 4 is scheduled for Wednesday. Both Lewiston games are slated to begin at 7 p.m. at the Androscoggin Bank Colisee.