Tournament medalist Megan Khang (USGA photo)

Although she prevailed in the end, for the first time in the championship, Khang, 17, of Rockland, Mass., wasn’t thrilled with her performance.

“I think this is actually my worst round,” said Khang, who is playing in a record-tying seventh U.S. Girls’ Junior. “It was definitely a good match, though. Shannon putted amazing today, and it was a great battle to have because she put me in a lot of pressure moments.”

Khang faced an early deficit when Brooks, 17, of Vienna, Va., won the fourth hole, but Khang evened the match on the next hole and won holes 8 and 9 to take a 2-up lead. Brooks pulled all square by winning Nos. 14 and 15, but Khang birdied the par-5 16th to recapture a lead that she maintained for the final two holes of the match.

“You always expect your matches to be tough because you never want to underestimate your opponent, and I knew Shannon was a great player,” said Khang, who will face fellow 17-year-old Naomi Ko, of Canada, in Thursday morning’s Round of 32. Khang’s best Girls’ Junior finish came in 2013 when she lost, 2 and 1, in the semifinals to eventual champion Gabriella Then.

After a back-and-forth match, Maria Balcazar, of Mexico, and Hannah O’Sullivan, of Chandler, Ariz., needed extra holes to determine a victor. Balcazar ended the battle with an exclamation point by holing out from 151 yards for an eagle on the par-4 first hole, earning the 19-hole victory. It was the second consecutive year that O’Sullivan, the 2015 U.S. Women’s Amateur Four-Ball runner-up, fell in the Girls’ Junior first round in extra holes.

“We saw it was a pretty good shot, and there were two people near the green who said, ‘wow,’ but we didn’t know it was in until I got to the green,” said Balcazar, who will face the long-hitting 2014 Girls’ Junior medalist Angel Yin, of Arcadia, Calif., on Thursday.

Yin, who is playing in her third Girls’ Junior, eliminated Pauline Del Rosario, of the Philippines, 4 and 2. Yin led by five strokes over 10 holes and carded an eagle on the par-4 13th hole, which was playing at 244 yards.

Malia Nam, 15, of Kailua, Hawaii, knocked off 2014 U.S. Women’s Amateur champion Kristen Gillman in a tight 2-and-1 match.

“We were going back and forth the whole round, and it wasn’t until the last couple holes that I was able to make some birdie putts,” said Nam, who didn’t realize she was playing the reigning Women’s Amateur champion. “I could see she was really trying to fight back, but it just didn’t work out. It was a really good match.”

Sophie Liu, the championship’s second seed, was defeated, 2 and 1, by Kathleen Scavo, who reached match play through Tuesday’s 10-for-7 playoff. Scavo, who will play for the University of Oregon in the fall, faces Ellie Slama, of Salem, Ore., in the Round of 32.

Alyaa Abdulghany needed 20 holes to eliminate Kendall Griffin, who earned medalist honors at the 2015 U.S. Women’s Amateur Four-Ball. It was a rematch of sorts, as Adbulghany and her partner Ellen Takada defeated Griffin and her partner Athena Yang in the quarterfinals of the Women’s Amateur Four-Ball.

Twelve-year-old Lucy Li, the championship’s youngest competitor, prevailed with a 6-and-5 victory against 16-year-old Pajaree Anannaruam. Li, who said today’s match was the best she’s played all week, will next face 13-year-old Karah Sanford.

Others to reach the Round of 32 include 2015 U.S. Women’s Open competitors Muni He and Maria Fassi, as well as the 2015 Pan American Games silver medalist Andrea Lee, 2015 U.S. Women’s Amateur Four-Ball champion Mika Liu and 2014 U.S. Women’s Amateur Public Links runner-up Eun Jeong Seong.

View results for U.S. Girls' Junior Amateur