PORTLAND — Spruce Mountain shut down Wells and broke away in the fourth quarter to earn a 38-24 victory in a Class B South girls basketball semifinal Tuesday at the Portland Expo.

The second-seeded Phoenix (19-1) advance to the B South final, where they face defending state champion No. 1 Oceanside (20-0) on Friday at the Expo.

The Phoenix are the first girls or boys basketball team from Spruce Mountain to reach a regional final.

“Definitely exciting because it’s the first time Spruce Mountain’s ever been there,” junior Olivia Mastine said.

In Tuesday’s game, Spruce Mountain held the third-seeded Warriors (17-3) to five second-half points, including just one point in the fourth quarter.

“Our defense definitely won us the game in the second half. Definitely,” Mastine said. “I think we just played harder and were more aggressive and went after the ball and just gave it our all.”

Spruce Mountain coach Zach Keene said that the Warriors broke down the Phoenix’s 1-2-2 zone too easily, which forced Spruce to switch to man-to-man in order to set up its half-court defense and make Wells work harder for its scoring opportunities.

“We kind of saw what that did in the second half, like, everything was hard on them,” Keene said. “(We) communicated at a high level, we guarded the ball, we rebounded at a high level — which was a concern coming into the game with a size difference.

“But, yeah, they were fantastic,” Keene said of the Phoenix. “That’s as good of a defensive half that I remember having. To do it in that situation speaks a lot about them.”

Mastine was a catalyst on both ends of the court for the Phoenix. On defense, she stole the ball or knocked it away from Wells ball handlers several times, she played physical against taller players and she chased down rebounds.

She also scored 11 of her game-high 13 points in the second half — seven of those in the fourth quarter.

After the Phoenix and Warriors went into halftime tied 19-19, Mastine said she tried to provide a spark for Spruce Mountain’s offense.

“Definitely needed to step up and play my game,” Mastine said.

Mastine scored the final four points of the third quarter to give the Phoenix a 26-23 lead.

She hit a pair of free throws for the first points of the fourth quarter. A minute later, she stole the ball and drove to the basket, where she was met by a couple of Wells defenders, so she passed the ball to Aubrey Kachnovich, who was trailing the play, and Kachnovich scored to increase Spruce’s advantage to 30-23 with 6:23 remaining in the game.

Mastine added two more baskets to complete a 12-0 run — Mastine scored 10 of the points and assisted on the other two — and the Phoenix’s lead was up to 34-23.

“I’ve come to expect that out of Olivia,” Keene said. “She’s unbelievably competitive, she’s cutthroat, she wants that pressure, she wants that moment. And as soon as she hit a couple early (in the second half), you could kind of feel it coming on, because we’ve seen it happen before.”

Kachnovich and Jaydn Pingree contributed eight points apiece for the Phoenix, while Elizabeth Grondin, Emily Dubord and Avery Bessey each made an important 3-pointer when the game was close.

Cali Leighton led Wells with 10 points, while Kendall Maxon had six.

Leighton scored six of her points in the first quarter, as the Warriors controlled both ends of the court, holding Spruce Mountain to five points and feeding the ball into the post, particularly Leighton, and building a 11-5 lead after one.

Spruced Mountain defended the post better in the second quarter, holding the Warriors to eight points while also starting to find a rhythm on offense.

In the first quarter, the Phoenix were limited to two baskets — a 3-pointer by Kachnovich and a field goal by Jaydn Pingree. Five Spruce players scored in the second, including four points by Pingree and 3-pointers by Bessey and Dubord.

Dubord’s trey tied the score at 16-16, and Bessey’s made it 19-19. Those were the final points of the half, and the teams went into the break even at 19-19.

Neither team scored in the first 3 minutes and 20 seconds of the second half, a drought that was ended by another Leighton basket.

Grondin hit a 3 to put Spruce Mountain up 22-21, its first lead since the early minutes of the opening quarter.

Leighton put the Warriors back in front 23-22 with another post bucket with about two minutes left in the third. That ended up being Wells’ final field goal of the game. After that, Mastine scored to start Spruce Mountain’s decisive 12-0 run.

Wells coach Sandi Purcell commended the adjustments that the Phoenix made in the way they defended the Warriors’ post players.

“I think that we were looking at our inside game a lot in the first half, and it was working really well,” Purcell said. “Then they went into halftime and adjusted kind of how they were playing our height, and every time we got it inside, two or three people were doubling down on our bigs, and we had a hard time adjusting to that double-, triple-team.

“So they did an awesome job adjusting, and then what was working for us in the first half wasn’t working, shots started to not fall.”

Purcell added that Wells’ inexperience also was a factor. The Warriors have only three seniors, and the rest of the players on the roster are sophomores or freshmen. That’s exciting for the future, but it made weathering the junior-laden Phoenix’s second-half run difficult.

“I think our youth showed a little bit, too, in the second half when they started to go on their run and we started to panic a little bit,” Purcell said. “Definitely, kind of showed that we have some experience to get under our belt before we make it to the big show.”

Last year, the Phoenix were a squad largely made up of underclassmen, and they received a learning experience in a B South semifinal loss to eventual state champion Oceanside. Now they get another shot at the Mariners, this time in the regional final, and they are the first team since Jay and Livermore Falls high schools combined in 2011 to become Spruce Mountain High School to advance this far in a basketball tournament.

“What an opportunity for us to have,” Keene said.