Hannah O’Sullivan, Mathilda Cappeliez, Sierra Brooks and Bethany Wu emerged victorious from Friday’s quarterfinal and have moved into Saturday’s semifinals at the 2015 U.S. Women’s Amateur Championship at Portland Golf Club.

O’Sullivan, 17, of Chandler, Ariz., survived a nail-biter of a match and earned a 1-up victory over Lindsey McCurdy, 20, of Liberty Hill, Texas. O’Sullivan had already notched three runaway victories through her match-play draw and she got off to a good start again on Friday, winning the second hole to grab an early 1-up advantage. But she stumbled with bogeys at holes 7, 8 and 10 to fall behind her opponent for the first time during the championship.

“I was getting a little frustrated out there, but I just had to collect myself and remember that it's only 2 down,” said O’Sullivan, who in February became the first amateur to win a Symetra Tour event since 1999 and the youngest winner in Tour history. “There’s so much golf left. It's really easy to turn a 2-down deficit around.”

And turn it around, she did. O’Sullivan reeled off a string of victories on holes 11-14 to build a 2-up lead, but had to drain a nervy 10-foot comebacker for par on No. 18 to claim her second consecutive U.S. Women’s Amateur semifinal berth. She punctuated the putt with a triple fist pump, something out of the ordinary for the normally reserved player.

“Inside, I'm really very competitive, and I guess I showed it a little bit there,” said O’Sullivan, the 2015 U.S. Women’s Amateur Four-Ball co-runner-up who has announced her intentions to attend the University of Southern California in 2016. “I really wanted to make that putt and just see it go in. It meant so much.”

Cappeliez, 17, of France, advanced with a smooth 5-and-4 win over Anna Newell, 19, of Tampa, Fla., and will meet O’Sullivan in Saturday’s first semifinal match. Cappeliez won the par-4 first hole with a birdie and then made par on the next 13 holes, extending her lead thanks to Newell’s bogeys on holes 6, 8, 12 and 14.

“I played solid golf and that was enough to win,” said Cappeliez, who is attempting to join Catherine Lacoste (1969) as the only Frenchwomen to win the U.S. Women’s Amateur. “I made some up-and-downs. I was twice in the bunkers, but I was always close to the holes, so that was easy. She (had) no birdies, so that was quite tough for her.”

Brooks, 17, of Sorrento, Fla., eliminated World No. 2 Bronte Law, 20, of England, 5 and 3. Brooks, who is competing in her first U.S. Women’s Amateur since 2012, found herself 1 down to Law, a two-time Curtis Cup competitor for Great Britain and Ireland, through four holes. However, she captured seven of the next 10 holes, including four with birdies, to win the match.

“Everything really did start to click and kind of started to separate there,” said Brooks, who plans to enroll at Wake Forest University in the fall of 2016.

Brooks’ next opponent will be Wu, 18, of Diamond Bar, Calif., who rolled to a 5-and-4 victory over 2015 U.S. Women’s Amateur Four-Ball co-champion Mika Liu, 16, of Beverly Hills, Calif. Wu, who came into the championship fresh off runner-up finishes in the 2015 North & South Women’s Amateur and Canadian Women’s Amateur championships, relied on her steady putting, winning the first three holes to quickly build a 3-up lead. She drained a birdie putt on the par-4 14th to seal the victory.

“I knew my putting had to be really, really good today,” said Wu, who will begin her freshman year at UCLA in late September. “She missed a few putts, and I missed a few, too. But, overall, I think I had the upper edge on that part.”

The Brooks-Wu semifinal meeting will be a meeting of great friends and a rematch of the 2014 Polo Golf Junior Classic semifinals, which saw Brooks squeak out a 19-hole victory over Wu before claiming the prestigious junior title.

“Bethany is actually my best friend,” said Brooks. “Anything can happen in match play, but if either one of us would win our match tomorrow, I'd be happy for both of us.”

The 2015 U.S. Women’s Amateur Championship is open to female amateur golfers with a Handicap Index® not exceeding 5.4. It consists of 36 holes of stroke play followed by six rounds of match play, with the championship scheduled to conclude with a 36-hole final on Sunday, Aug. 16.

The match-play rounds of the 2015 U.S. Women’s Amateur Championship will be broadcast on Fox Sports 1. Coverage will be from 4 p.m. to 7 p.m. EDT every day through Sunday, Aug. 16. Additionally, bonus coverage will be streamed live on usga.org on Aug. 16 from Noon to 2 p.m. EDT.

The U.S. Women’s Amateur Championship is one of 13 national championship conducted annually by the United States Golf Association, 10 of which are strictly for amateurs.

Christina Lance is a manager of championship communications for the USGA. Email her at clance@usga.org.