PORTLAND — The Kings conquered all comers during its best-ever season — except one.

For the third time this season, Cheverus/Yarmouth won a matchup between the two teams, and Wednesday’s 3-1 loss in the Class B South final at Cross Insurance Arena was the most deflating for the Kings.

Poland/Leavitt/Oak Hill/Gray-New Gloucester, formed before the 2016-17 season with Kings as its collective mascot, took a 15-game winning streak into Wednesday night’s Class B South final — the first regional final for any of the schools involved. The Kings suffered only three losses during the regular season, and got revenge for one of those with a semifinal win over York.

The other two losses to Cheverus/Yarmouth came in December within the Kings’ first four games of the season, both by 3-1 scores.

“We work on team defense from day one in camp, and we work at it every day,” Cheverus/Yarmouth coach David St. Pierre said. “We game plan specifically against how we wanted to defend this team, and the boys did a great job executing. So it was kind of a team effort here.”

In the teams’ third and most important meeting, second-seeded Poland/Leavitt/Oak Hill/Gray-New Gloucester (17-4) was without top scorer Will Keach due to injury.

After a scoreless first period — in which the Kings had a 10-6 advantage in shots on goal — top-seeded Cheverus/Yarmouth’s (17-2-2) Owen Walsh broke the ice 3:23 into the second period, skating in alone and sending a shot from the right circle past Kings goalie Ian Guerin.

“I think the first period for us was all nerves. … We just kind of tried to calm them down and get them to relax, get back to our game plan. And to their credit, they responded really well,” St. Pierre said. “They put the compete hat on. We went back into our defensive structure, and they did a much better job keeping them away from the net. And we ended up capitalizing on some chances.”

Poland/Leavitt/Oak Hill/Gray-NG’s Brody Emond had a pair of point-blank chances a few minutes later, but was denied by Cheverus/Yarmouth goalie Ethan Tucker both times. First, Emond tried a wraparound that Tucker stuffed up into the air before the puck left the goal area. Moments later, Breck Langevin’s pass from the right boards made it to Emond to the left of the goal, but Tucker stopped Emond’s re-direct.

“They protect the house in front of the net well,” Kings coach Jason Rouleau said. “You know, we were able to get some shots off. We had 30-some-odd shots on net. But they defend the second-chance opportunities really well. And they took those opportunities away from us, which normally we capitalize on a couple of those in a game.”

The Kings went on their first power play with just over five minutes left in the middle frame, but after a good initial chance, Cheverus/Yarmouth cleared the puck and suffocated the Kings in their own end for an extended period before killing the penalty off for good.

Cheverus/Yarmouth then nearly squandered its own power play with under two minutes to go before the second intermission.

First, the Kings’ Conner Boulay poked the puck away in his own defensive zone and skated up the ice for a shorthanded breakaway, only for his shot to miss the mark.

It looked like the Kings might survive the period still down just one goal, but with five seconds left, Andrew Cheever fired a shot from the right circle that beat Guerin to make it 2-0. Walsh was credited with the assist.

“It’s a great example of how this team has come together and they feed off of each other,” St. Pierre said. “I think everybody knew Ethan was going to make that save. We were there to collect the rebound, and we moved it up quickly because we knew we could counterattack. And so that’s great recognition on our guys’ part, and Cheever’s part, to kind of race up ice and pick a hole on the goalie. So I thought that was a great response from a team standpoint.”

Rouleau called it the prototypical backbreaker goal.

“Yeah, it’s hard, but our boys have been mentally tough all season. It’s not the first time they had to overcome adversity,” he said. “And we came out, and we gave it everything we had. We had multiple scoring opportunities in that third period, we capitalized on one. We just didn’t capitalize on enough.”

The Kings cut their deficit to one late in the third period. Parker Pelletier put back in a rebound of Luke Gladu’s point shot off the post with one second left on a power play. That put the Kings down 2-1 with 3:42 left.

The Kings called their timeout with 1:06 left, giving them a chance to pull Guerin with an offensive zone faceoff upcoming. The plan put in place never had a chance, as Quinn McCoy blocked a point shot, then took the puck the other way for an empty-net insurance goal with 59 seconds left.

Guerin finished with 15 saves. Tucker, who St. Pierre said had probably one of his best games of the season, stopped 23 shots for Cheverus/Yarmouth, which faces North champ Camden Hills Saturday at Cross Insurance Arena.

“This is the fourth year of the program, this is the only program these boys have known — the seniors,” St. Pierre said. “And they’ve built the culture. And we’ve gotten close the last two years. … So we’ve been snipping at it. And they know, they know we’ve been close.”

KINGS MISSED KEACH

The Kings scored three-plus goals in every game this season that wasn’t against Cheverus/Yarmouth. Keach’s Class B South-leading 48 points (23 goals, 25 assists) during the regular season were a big part in that, but St. Pierre said the Kings were more than a one-player team.

“They’re a very talented team. They got a lot of depth — offensively, especially. Very dangerous team offensively,” St. Pierre said. “And we knew they were going to rally (without Keach).”

St. Pierre said the Kings trying to fill the void of missing Keach — who Rouleau said got hurt in the regional semifinal win and was confirmed out for the rest of the season Tuesday — probably played a part in the Kings coming out with the first-period momentum.

Rouleau said the team’s response to not having Keach was “huge.”

“I mean, you know, the entire team stepped up. It wasn’t one individual who stepped up, it was the entire team,” he said. “At the end of the game, I pulled the boys in and said, ‘I’m proud of the effort you guys put forth today. You need to be proud of the effort you guys put forth.’ Sometimes you don’t come out on top, and we’ve got to learn how to handle that.”

Rouleau admitted not having Keach, who on Wednesday was named a nominee for the Evans Spear Award that goes to the most outstanding senior player in Class B South, was hard for the Kings to overcome.