Caroline Wozniacki survived her first test of the tournament to underline her status as top seed at the US Open with a fourth-round victory over former champion Maria Sharapova.
Wozniacki had dropped just three games in her first three matches at Flushing Meadows but knew Sharapova would present a far tougher proposition.
However, the 20-year-old Dane produced a typically assured performance to win 6-3 6-4 and book a quarter-final clash with the unseeded Dominika Cibulkova, who beat another former champion, Svetlana Kuznetsova, 7-5 7-6.
“It was a really tough match, Maria is a great player so I knew it wasn’t going to be easy,” said Wozniacki, who reached the final here last year where she lost to Kim Clijsters.
“Reaching the final last year definitely helped me a lot, I got a lot of experience from last year and I’m just so happy that I won today and am through to the quarter-finals.
“I definitely think I’ve improved a lot, not only physically, but also I believe in myself more. I believe I can do it. Also I think I can mix up my game a little bit more than I could last year.”
Sharapova was let down by her serve and too many basic mistakes, the 14th seed serving nine double faults and committing 36 unforced errors compared to just 10 from Wozniacki.
The 23-year-old served three double faults in a row to lose her serve early in the first set, and although she clawed that break back, she promptly lost serve again in the next game to allow Wozniacki to serve out for the set.
And another double fault proved crucial in the second set, gifting Wozniacki the break she need to complete an impressive win.
“Even with those unforced errors I still had my chances and I was one for eight on break points,” Sharapova said. “Against someone that’s playing really well, playing with a lot of confidence, it’s really important to take those chances that you have, the very few that come your way.
“I felt like I played a couple of good points and then made an easy error, hit a return long or missed a first serve. I didn’t feel like I put much pressure on her.”
At 45th in the world, Cibulkova is the lowest ranked player remaining in the draw, but the 21-year-old shrugged off her poor summer form to secure a 7-5 7-6 (7/4) victory on Arthur Ashe Stadium.
Cibulkova had not won back-to-back matches in six tournaments since Wimbledon before arriving in New York, but won her first two matches at Flushing Meadows in three sets before dropping just one game in beating Lourdes Dominguez Lino in the third round.
“I was really working hard for this and I had tough times,” Cibulkova said. “So I was really pumped for this. I know my game and I know myself, so I knew I could make it. I could beat everybody in this tournament. I was just waiting for a moment and I’m happy it’s here.”
Estonia’s Kaia Kanepi also advanced to the quarter-finals after an extraordinary comeback against 15th seed Yanina Wickmayer of Belgium.
Kanepi, who knocked fourth seed Jelena Jankovic out in the previous round, lost the opening set without winning a game but stormed back to win 0-6 7-6 (7/2) 6-1 in two hours 21 minutes.
The 31st seed, who also reached the quarter-finals of Wimbledon this year, made 46 unforced errors in the match, but crucially only six in the decider as she set up a last-eight clash with seventh seed Vera Zvonareva, who eased past Andrea Petkovic 6-1 6-2.