SOUTH DEERFIELD — After 80 minutes of close calls and near misses from both sides, Ethan LaFleur finally put a stop to it in 31 seconds.

LaFleur’s unassisted tally in the first minute of sudden-death overtime propelled fourth-seeded Frontier Regional to a 1-0 victory over fifth-seeded Pope Francis in the quarterfinals of the Western Massachusetts Division 3 Boys Soccer Tournament Tuesday night at Frontier.

“That was an amazing game,” Red Hawks coach Dale Totman said. “I thought both teams played extremely well. I honestly thought was about as even as you could get.”

Frontier (11-3-4), the defending champion, advances to play No. 1 Hampshire Regional (14-2-1) in the semifinals on Thursday at 7 p.m. at South Hadley High.

The winning play in the extra session started innocently enough with a chip into the Cardinals penalty box. However, the dew-covered ball slipped through the gloves of Pope Francis goalkeeper Liam Sears, and a mad scramble ensued 15 yards from goal.

Red Hawk midfielder Ian Newman’s first attempt was blocked, but LaFluer spotted the loose ball squirt away from the throng, got to the ball first and booted it into the open corner for his 14th goal of the season to set off a wild celebration.

“The margin (for error) is that thin, their goalie made a mistake and we were able to capitalize,” said Totman. “A lot of (LaFleur’s) goals are very scrappy. He’s that type of forward you want. He’s always first to the ball. That was a typical Ethan goal.”

It was also one that the Red Hawks were fortunate to experience. The Cardinals held a 60-40 edge in possession, outshot Frontier 16-11 and had the lion’s share of quality scoring chances.

A Pope Francis goal was disallowed due to a foul in the goal box in the first half, and the Cardinals were awarded a penalty kick when Sam Schecterle was called for a hand ball in the penalty area.

Pope Francis forward Cam Peritz tried to place the ball into the corner to Frontier goalkeeper Peter Bronke’s left, but Bronke made a diving save, and the follow-up attempt by Cardinals midfielder Makem Demers from point-blank range went over the bar.

“Peter has been amazing all year,” said Totman. “Honestly, I thought he was going to save it. It honestly didn’t surprise me. He’s only a sophomore, and to come up with that save in that moment is huge.”