ATHOL, Mass. -- Senior Arianna Walden has made a lot of big plays for the Mount Greylock girls basketball team over the years.

But arguably none were bigger than what she did at the foul line in the closing moments of Monday’s 52-43 Western Mass Division 3 tournament win.

With 47 seconds left to play, Walden went to the foul line for a one-and-one opportunity with her team up, 47-43. She calmly hit both shots to extend the lead to six points.

Eighteen seconds later, after an Athol turnover, Walden again was fouled and again had to shoot one plus the bonus. She hit both for her 18th point of the game and a seemingly insurmountable eight-point lead.

After Jenna Benzinger grabbed her 16th rebound of the game at the other end, Lauren Howard hit the front end of he one-and-one to provide the final nine-point margin of a win that sends the ninth-seeded Mounties (14-7) into the sectional quarterfinals on Thursday at top-ranked South Hadley (19-1).

“Those were pretty big opportunities,” Walden said of the late foul shots. “It put us under a lot of pressure. But it was really great to know that under pressure I can do do those things and I can pull through when we need it the most.”

Walden and Benzinger came up big in big moments all night. The former scored a game-high 18. The latter poured in 16 for a double-double and blocked six shots.

But both also ran into foul trouble, eventually earning their respective fourth personals in the third quarter.

“Jacqui Byrnes did a good job stepping up,” Mount Greylock coach John Jacobbe said. “She didn’t score any points for us, but she played strong defense. … Our subs either kept the lead or extended it.

“Our bench did a good job today. I have confidence in our bench today, and they stepped up. We play nine or 10 deep, usually. Rachel Voller only got in for a couple of minutes, and she got a steal doubling on [Emily] Casella. It was a good team effort.”

Casella scored 15 points for eighth-seeded Athol (12-9). Hope Parker scored a team-high 16.

Both did most of their damage in a second half that saw the hosts bounce back from a 37-20 deficit early in the third quarter to tie it, 39-39, with about seven minutes left in the fourth.

The 19-2 could have spelled the end for a lot of tournament underdogs, but with 5 minutes, 26 seconds left to play, Benzinger hit a bucket in the post. And moments later, Walden set up Howard for a press-breaking lay-in to make it a four-point lead again.

It was a two-point lead with just more than a minute left when Mount Greylock sophomore guard Caroline Flynn - another reserve - made a move on the baseline and scored in the post to make it 47-43, setting the stage for the foul shots to come.

“Caroline Flynn made a huge bucket,” Jacobbe said. “Good for Caroline. She had a head injury early in the year. And tonight she played one of her best games of the year. I’m really proud of the effort she put in as she battled back from her injury.”

Mount Greylock built its with a 20-8 third quarter that saw Walden score 11 points — six on 3-pointers. Howard also hit a 3 and grabbed some big rebounds on her way to a 10-point, nine-rebound night.

The Mounties again will need all hands on deck Thursday when they play South Hadley for a ticket to Curry Hicks Cage.

“We should be loose as a goose and just play with everything we have because we’re playing a 19-1 team,” Jacobbe said. “Don’t be intimidated. Just go up there and show them everything we have and take our chances. Make the No. 1 seed beat you. Don’t just lay down because they’re the top dog.”