SYDNEY (AP) — Top seed and defending champion Agnieszka Radwanska of Poland was defeated by American qualifier Bethanie Mattek-Sands 7-5, 6-3 in the second round of the Sydney International, a key warm-up tournament for the Australian Open.
Mattek-Sands, who is back on tour after a four-month layoff because of a right knee injury, lost in the first round in Brisbane last week and had to win three matches just to qualify for the main draw in Sydney.
"Very happy with it," Mattek-Sands said. "I've played her a couple times and I've never beaten her, so it's probably one of the best wins of my career."
Radwanska received treatment on her right serving shoulder during last week's Hopman Cup in Perth and said Tuesday it was still bothering her.
"Maybe a little bit, but I have good painkillers," Radwanska said. "It's not a big deal, it should be all right."
Mattek-Sands advanced to play fellow American Madison Keys, who defeated Croatian wild-card entry Ajla Tomljanovic 6-0, 3-6, 7-6 (3).
Former No. 1 Caroline Wozniacki was also on the receiving end of an upset, falling to Lucie Safarova 6-4, 7-6 (7). Wozniacki, recently engaged to golfer Rory McIlroy, was up three points in the second-set tiebreaker before allowing Safarova to clinch the match.
Former Wimbledon champion Petra Kvitova, the second seed, had little trouble in the afternoon session, beating American qualifier Christina McHale 6-1, 6-0. Angelique Kerber of Germany was also through to the quarterfinals after beating Kaia Kanepi of Estonia 6-3 6-4.
In other men's play at Sydney, defending champion Bernard Tomic of Australia advanced with a 6-3, 6-0 win over eighth-seeded Marcel Granollers of Spain.
Seventh-seeded Marin Cilic of Croatia defeated Jan-Lennard Struff of Germany 3-6, 6-3, 6-3, Spain's Albert Ramos took out American Sam Querrey 4-6, 6-3, 6-4, and Nicolas Mahut of France beat American Ryan Harrison 7-6 (2), 7-5.