Thailand's Ariya Jutanugarn won two matches Thursday in the U.S. Women's Amateur to advance to the quarterfinals at The Country Club.

The 16-year-old Jutanugarn, coming off a successful title defense last week in the Junior PGA Championship, routed Bethany Wu of Diamond Bar, Calif., 6 and 4 in the morning, and edged Australia's Ashlee Dewhurst 3 and 2 in the afternoon in the round of 16.

Jutanugarn, also the 2011 U.S. Girls' Junior champion, will face Erynne Lee of Silverdale, Wash., in the quarterfinals. Lee, one of two U.S. players in the final eight, beat Elisabeth Bernabe of Anaheim Hills, Calif., 3 and 2, and Austin Ernst of Seneca, S.C., 2 and 1.

"I'm not really thinking about Ariya," said Lee, coming off her freshman season at UCLA. "I know I have a pretty good resume. But now I'm not too tired after winning. I have an adrenaline rush."

In the other lower-bracket quarterfinal, New Zealand's Lydia Ko will play South Africa's Paula Reto, the oldest quarterfinalist at 22.

The 15-year-old Ko, the top-ranked amateur in the world, scrambled out of deep rough for a halve on the 18th hole to outlast France's Celine Boutier 1-up for a spot in the quarterfinals.

"It was lucky," Ko said. "If I go in that bunker, it's a hard shot."

In the upper-bracket quarterfinals, Canada's Nicole Zhang will face Australia's 16-year-old Su-Hyun Oh, and Jaye Marie Green of Boca Raton, Fla., will play Mexico's Marijosse Navarro.

Zhang beat qualifying medalist Hyo-Joo Kim of South Korea 1-up in the round of 16.

"I found it a lot more difficult because it was so wet," Zhang said about the course, softened my morning rain. "I managed to get it up and down and I've definitely liked my game the last few days."