Briton Heather Watson produced an upset at the ASB Classic in Auckland by knocking out ninth seed Carla Suarez Navarro.
In doing so, the 18-year-old from Guernsey - playing as a qualifier in New Zealand - reached her first WTA Tour quarter-final, where she will meet China's Shuai Peng.
Watson was good value for her win, beating the Spaniard 7-6(7/5) 6-1. She was broken three times in the first before clinching it in the tie-break and world number 57 Navarro struggled in the second set as Watson capitalised on her momentum.
"I'm so pumped to be in the quarter-finals here in Auckland!" Watson said on Twitter. "I played really well today."
Top seeds Maria Sharapova and Yanina Wickmayer also moved into the quarter-finals.
Russian Sharapova came from behind in both sets to beat Renata Voracova 6-3, 7-5. Voracova had been 3-1 up in the first and 5-3 in the second but conspired to lose both as Sharapova dug deep.
Second seed Wickmayer needed three sets to overcome qualifier Sabine Lisicki, winning 6-2, 3-6, 6-2. Svetlana Kuznetsova, the number three seed, fell to Peng Shuai 2-6, 6-4, 6-4.
Elsewhere, Roger Federer produced a no-frills display against compatriot Marco Chiudinelli to reach the Qatar Open quarter-finals.
After thrilling the crowd on Tuesday with one of his "between the legs" trick shots, the Swiss world No 2 laboured to a 7-6, 7-5 victory in one hour 48 minutes.
Third seed Jo Wilfried Tsonga of France, making his comeback from injury, moved into the quarter-finals with a 6-2, 6-4 defeat of Ukraine's Sergei Bubka.
Marion Bartoli reached the quarter-finals of the Brisbane International after watching her fellow seeds bow out.
Third seed Nadia Petrova had exited in the first round and Samantha Stosur and Shahar Peer, first and second seeds, fell in the second round. However, fourth seed Bartoli progressed but needed three sets to defeat Iveta Benesova, eventually winning 6-1, 3-6, 6-0.
In the men's draw, Andy Roddick weathered an early onslaught from hard-hitting Ukrainian Alexandr Dolgopolov before beating him 6-4, 6-1 to set up a quarter-final clash with Marcos Baghdatis.
The 22-year-old Dolgopolov attacked Roddick's serve to win an early break and go up 4-2.
The American world No 8 quickly broke back, however, and reeled off 10 of the final 11 games to seal the match in less than an hour.
"I knew that he was aggressive," he said of Dolgopolov. "He came out in the first six games and I didn't do much wrong. When someone is going to try and hit a winner from whatever ball they get on the first shot, and if they convert, there's very little you can do.
"It was my plan to make him come up with those shots for the better part of a couple of hours and it caught up to him a little bit."
Fifth seed Baghdatis beat Poland's Lukasz Kubot 6-2, 6-2 and was relishing the prospect of meeting Roddick today.
"It's nice to play guys like Andy," the former Australian Open finalist said. "It's a test match before the Australian Open and it will be a great match."
Sixth seed Feliciano Lopez was defeated 6-3, 6-1 by unseeded South African Kevin Anderson.
In the Hopman Cup mixed event, Great Britain crashed out at the group stage as Andy Murray and Laura Robson were defeated in the decisive mixed doubles rubber against France.
Nicolas Mahut and Kristina Mladenovic won 6-4, 6-2 to give France a 2-1 victory. Robson had earlier lost the opening singles 6-4, 3-6, 6-0 to Mladenovic, before Murray gave his team hope with a 7-6 (7-3), 7-6 (7-5) win over Mahut.
Britain will take on the United States in their last Group B match but cannot qualify for the final following an earlier defeat to Italy.
Caroline Wozniacki, the world No 1, beat Li Na of China 6-4, 6-3 at the Hong Kong Classic exhibition tournament.