Rafael Nadal
Rafael NadalReuters

Rafael Nadal has reached the quarterfinals of the 2014 Australian Open by beating Japan's Kei Nishikori in straight sets on Monday, though it was a far from comfortable outing for the Spaniard.

Nadal was pushed hard by the 16th seed in all three sets, though the world number one eventually came out on top with a 7-6 7-5 7-6 victory at the Rod Laver Arena.

The Spaniard, who had not been broken in the previous rounds, dropped four of his service games, before managing to end the challenge from Nishikori in a match that lasted three hours and 17 minutes.

The win sets up Nadal for a clash with Bulgaria's Grigor Dimitrov in the quarters on Wednesday.

Nadal is looking to win the Australian Open for the second time and secure the 14th Grand Slam title of his career, to equal Pete Sampras and go just three behind Roger Federer's record tally of 17.

Also through to the quarters is fourth seed and British number one Andy Murray, who beat luck loser Stephane Robert of France in four sets.

The Scot eased through the first two sets but Robert won the third set in tiebreaker, though Murray bounced back in the fourth to win 6-1 6-2 6-7 6-2.

Meanwhile, India's Rohan Bopanna won his second round mixed doubles match to enter the Australian Open quarterfinals.

Bopanna and his Slovakian partner Katarina Srebotnik, seeded second, overcame unseeded Australian pair John Peers and Ashleigh Barty 7-6 7-5 at the Hisense Arena.

The Indo-Slovak pair will once again face an unseeded local duo in the quarters, as they have been drawn against Matthew Ebden and Jarmila Gajdosova in the last eight.