Buffalo Grove coach Steve Kolodziej had a message for freshman Maddie Welter at practice Saturday.

“My coach told me whenever he put me in the game, he wanted me in there to score points,” said Welter, who nine months ago was a student at Thomas Middle School in Arlington Heights. “So I kind of thought on that.”

Whatever she was thinking, it couldn’t have worked out better.

Welter came off the bench to score a career-high 19 points and help No. 15 seeded Buffalo Grove claim a 59-52 victory over No. 19 Lake Zurich in Monday’s play-in game of the Class 4A Fremd girls basketball regional.

The Bison (10-17) advance to today’s semifinal against No. 3-seed Fremd (23-7) at 6 p.m. The second semifinal at 7:30 p.m. matches No. 7 Barrington (15-14) and No. 10 Prospect (14-12).

“That No. 3 (Welter) hit some real nice jump shots,” said Lake Zurich coach Chris Bennett, whose team finished at 5-22. “And their No. 4 (sophomore Julie Jambrone who had 10 points with a 3-pointer) did a great job going to the basket. We didn’t get good rotation help-side defense.”

BG’s other double-figure scorer was sophomore Madeline Callanan (11 points, two 3-pointers, 5 rebounds), meaning a freshman and two sophomores combined for 40 of the Bison’s 59 points.

Welter, who joined the varsity team in mid December, had two 3-pointers and was 5-of-6 at the free throw line.

“Maddie just stepped up and seized the moment,” said Kolodziej of his rookie guard whose previous career best was 11 points against Naperville Central. “She had a great game. That’s the type of player she is offensively. One thing she does is score.”

BG trailed 14-11 but Jambrone’s curl for a driving bank shot got BG to within 19-16 after one quarter.

Two free throws by freshman Abby Pirron gave the Bears their biggest lead at 26-20.

BG, though, used a 9-2 run to take the lead at 29-28 when Welter fired home a 3-pointer with 1:39 left in the half.

A 15-footer by senior Kayla Stavnes gave LZ a 30-29 lead at intermission.

Stavnes is one of three seniors for the Bears.

The rest of Bennett’s 16-player roster on Monday consisted of freshmen and sophomores.

“As they always do, our three seniors played their hearts out,” Bennett said. “Kayla gave us good minutes. Sara Gazdacka and Sarah Stefaniu give you everything they’ve got every day. I would have liked for all them to get a win. But Buffalo Grove just scored a few more baskets than us.”

Bennett also liked the work of 5-foot-7 sophomore Rachel Dawson.

“I thought Rachel did an outstanding job going up against Bailey North (BG’s 6-foot senior),” he said. “She was giving up two years and four inches but she battled every step of the way.”

Stefaniu’s steal and layup to start the second half put the Bears ahead 32-29 but BG never fell behind by more than 3 points.

When Stefaniu drilled a 17-footer from right of the key, the game was tied at 38.

That’s when the Bison made their big move by scoring 7 unanswered points in the final minute of the third quarter.

A 3-pointer by Jambrone, rebound bank shot by Mary Zawlocki and fastbreak layup by Brianna Kolbus made it 45-38.

Lake Zurich refused to surrender and pulled to within 45-42 on a 3-pointer by Gazdacka.

After a beautiful spin move by Jambrone for a layup made it 47-42, North (6 points) fouled out with 5:35 left in the game.

The senior, who scored her 1,000th point last week, also suffered a sprained hand.

“The one thing about Bailey is she’s always played hurt,” Kolodziej said. “The poor kid has been banged up her entire career. She knows better than anyone how to prepare. She’s a competitor and she always seems to find a way to compete.”

With North on the sidelines, Lake Zurich pulled to within 47-46 on a 16-footer by Stefaniu.

“We all knew we had to step up without Bailey,” said Welter, whose 3-pointer made it 50-46 with 4:05 left in the game.

The Bison outscored the Bears 12-6 in the final four minutes.

Amanda Salzman (7 points, 7 assists, 3 rebounds, 3 steals) hit 2 free throws to ice the game with 16.7 seconds left, making it 59-52.“Amanda did a great job running our offense,” Kolodziej said. “Mary Zawlocki (6 rebounds) was excellent with her rebounding and defense and Alyssa Mills (3 rebounds) gave us quality minutes as she always does and did a great job rebounding.

“I was really happy with everyone’s effort after we lost Bailey. Lake Zurich was no longer getting easy baskets. The one thing about these girls is that they have always responded to adversity. We’ve practiced a lot of these scenarios all season and how to finish games, and it paid off this time.”