SCARBOROUGH — Neither Scarborough nor South Portland had allowed a goal all October, so it was no surprise to see their Class A South boys’ soccer quarterfinal scoreless through 76 minutes Tuesday night.

“You got the feeling on either side,” Scarborough Coach Mark Diaz said, ” it would take one of those shots that’s almost unsavable.”

Enter Scarborough senior Noah Stracqualursi, who made a run down the right side of the field until he ran out of real estate within a few feet of the end line. He stopped abruptly, pivoted away from the goal and with his left foot sent a pass across the goal mouth toward a teammate streaking to the far post.

“I was crossing it back post,” Stracqualursi said, “and luck was with me, honestly.”

Indeed, the ball looped over the head of South Portland goalie Riley Hasson and nestled into the upper left corner of the net to give the fourth-seeded Red Storm a 1-0 victory over the No. 5 Red Riots.

Scarborough (12-3) advances to Saturday’s regional semifinal at No. 1 Gorham, a 4-0 winner over No. 9 Westbrook. South Portland, which had won 10 in a row including seven straight shutouts, finishes 12-4.

“That’s a one-in-a-million shot,” South Portland Coach Bryan Hoy said. “There’s no way a keeper gets to it. It’s a beautiful play. That’s a successful season if that’s what it takes to beat us.”

Scarborough held a 12-1 advantage in shots on goal and 6-1 edge in corner kicks but had trouble penetrating South Portland’s back line of Pat Graff, Riley Ellis, Jacob Milton and Brandon Gagne. With five minutes remaining, Scarborough senior Garrett King sideswiped a shot that got past Hasson but Gagne, from the goal line, headed it away from danger.

“They had a great clear,” King said. “But we felt it coming. Once a few people step up and give the energy, it’s inevitable really.”

South Portland’s only shot on Scarborough goalie Chris Franklin came 11 minutes after halftime when junior striker Charlie Cronin dribbled around two defenders and sent a low shot near the right post. Franklin easily scooped it up.

“They played fantastic as a unit,” Diaz said of Scarborough defenders Alex Giles, Matt Blaisdell, Nick Anderson and Spencer Pettingill. “They have some good forwards on that (South Portland) team who are very dangerous and I thought overall we did a good job containing them.”

Hasson finished with 10 saves to Franklin’s one. South Portland midfielders Khalid Suja and Aleks Kaurin had plenty of possession time from about 25 yards away from the Scarborough goal but couldn’t figure out a way to generate a decent scoring chance.

“Their counterattack was two guys,” South Portland’s Hoy said. “That makes it really difficult to score, when they’ve got nine guys in the box.”

Finally, with just 3:09 remaining, Stracqualursi solved the South Portland defense for the first time.

“In practice, we just work on getting it as close to the back post as possible,” Stracqualursi said. “It was just a little bit closer to the goal than to the player I was going to.”