MELBOURNE, Australia (AP) — Two-time defending champion Victoria Azarenka saw another of her main adversaries crash out of the Australian Open on Monday, while top-ranked Rafael Nadal and Wimbledon champion Andy Murray faced tougher-than-expected matches to advance to the quarterfinals at Melbourne Park.
Maria Sharapova joined Serena Williams as fourth-round casualties, leaving Azarenka a potentially easier run to the women's final. Sharapova was beaten by No. 20 Dominika Cibulkova in the match on Rod Laver Arena immediately before Azarenka defeated Sloane Stephens, the last remaining American in the singles draw.
Nadal won three tough sets against Kei Nishikori, while Murray wasted four match points in the third set — including two in the tiebreaker — before dominating the fourth set against lucky loser Stephane Robert of France.
Four-time Australian Open champion Roger Federer was never threatened in beating 2008 finalist Jo-Wilfried Tsonga 6-3, 7-5, 6-4 in a late match. He will play Murray in the quarterfinals on Wednesday.
Third-seeded Sharapova, complaining of a hip ailment, lost 3-6, 6-4, 6-1 after struggling with her serve and making 45 unforced errors. She joins Williams on the sidelines after the top-ranked American lost in three sets Sunday to Ana Ivanovic, ending 25-match winning streak.
Sharapova had spent the latter months of last year on the sidelines with a right shoulder injury, so she wasn't expecting much of herself.
"I have to look at the positives and see where I have come from in four or five months," Sharapova said. "I haven't played a lot of tennis. "
Azarenka had a 6-3, 6-2 win over No. 13-seeded Stephens, the player who beat Williams in the quarterfinals here last year and then lost to Azarenka in the semifinals under controversial circumstances. Azarenka took a medical time out when Stephens started to gain momentum in that match, then came back to advance to the final and subsequently win her second Australian Open trophy.
She wasn't getting carried away Monday with the apparent ease of the draw with Williams and Sharapova gone.
"The players who beat those players deserve all the credit because they've been better, so they are dangerous and they are competitive," Azarenka said.
Azarenka, who is on an 18-match winning streak at Melbourne Park, will next play No. 5 Agnieszka Radwanska, who beat Spain's Garbine Muguruza 6-1, 6-3 in the final fourth-round match Monday night.