After 76 scoreless minutes in a Class A South boys’ soccer quarterfinal Tuesday night, Deering found the back of Portland’s net.

Robert Ochan headed in a corner kick that would have given the Rams a 1-0 lead with 3:19 remaining.

But an offside call negated the goal and Alex Frank scored the winner for Portland with 40 seconds remaining for a 1-0 victory at Deering High.

The sixth-seeded Bulldogs (11-3-1) will be at second-ranked Falmouth (12-2-1) in the semifinals Saturday.

“The rivalry goes very deep in this city,” Portland Coach Rocco Frenzilli said. “It was a great game played by two very evenly matched teams. It just so happened that the ball rolled our way.”

Ochan’s goal was the second called for offside for third-seeded Deering (11-2-2). Orey Dutton apparently scored in the first half on a breakaway, when his shot bounced back to him off Portland goalkeeper Rowan Daligan. Dutton put it in before the call.

Deering Coach Joel Costigan said he couldn’t see if the call was correct but felt differently about the second offside.

“The second one, I can’t fathom how that’s offside,” Costigan said. “Coming off of a corner kick, the guy who plays the ball is not offside.”

The winning goal came when Samuel Nkurunziza crossed the ball from the right corner and Frank placed it in the net.

“We worked the ball down the side, which we had been going for all day,” Frank said. “I stepped up, saw the ball on the ground and struck it home.”

The first half was back and forth, with each team taking four shots.

Portland had the edge in the second half, outshooting Deering 7-4.

“I thought, in the second half, we were able to move the ball down the sides and cross,” Frenzilli said, “and that was the play at the end that got us there.”

Louange Turahimbawe of Deering nearly scored two minutes into the second half when his shot bounced off the crossbar.

Three minutes later, a Nkurunziza shot was deflected by a defender before Deering goalkeeper Mustafa Kadhim made the save.

“Their defense is unbelievable,” Frank said. “I know (defender) Jonata (Mbongo) is a great kid who works really hard – I definitely think getting one against him is a tough thing, and – thankfully – we were able to do it.”

Costigan also noted the efforts of Caleb Delano and Iessa Ramadan in the Rams’ defense.

After the Bulldogs and Rams tied 1-1 on Oct. 18, Costigan said he came in with a game plan of playing containment defense on the outside – which involved having Deering’s outside backs cover Portland’s wings one-on-one while playing with a man-mark in the middle of the field.

“The problem playing with a man-mark system is when we break down, that man is open,” Costigan said. “The man got open once and he scored.”

Kadhim finished with five saves and Daligan had three.

“I’m just pleased with how we were able to fight and not give up,” Frank said. “Both teams had opportunities. It was just a matter of who was able to put one in first.”

CORRECTION: This story was updated at 10:45 a.m. on Oct. 28 to clarify Deering’s defensive strategy.