Intro:

World number one through to last eight as other top seeds crash out of tournament.

Script:

Rafael Nadal advanced to the quarter-finals of the Australian Open on Monday after a 7-6 (3), 7-5, 7-6 (3) win over Kei Nishikori of Japan.

Nadal is trying to win the Australian Open for the second time - his first title came in 2009 - and secure the 14th major of his career, equal with Pete Sampras and three behind Roger Federer's leading total of 17. The Australian Open is the only major he hasn't won at least twice.

In the women's singles, Maria Sharapova followed Serena Williams out of the tournament after the second fourth-round upset in 24 hours.

Third-seeded Sharapova lost 3-6, 6-4, 6-1 to Dominika Cibulkova,

With Sharapova and Williams out, Victoria Azarenka is now a firm favourite to claim a third successive Australian Open title.

She advanced to the quarterfinals with a 6-3, 6-2 win over 13th seed Sloane Stephens.

Meanwhile former world number one Jelena Jankovic fell by the wayside when the 11th seed, Simona Halep of Romania, beat her 6-4, 2-6, 6-0.

Halep will now face Cibulkova in the last eight.

In the men's doubles Bob and Mike Bryan had a shock defeat to Eric Butorac and Raven Klaasen 7-6 (9), 6-4.