DEFENDING champion Rafael Nadal set up a blockbuster quarter-final against Andy Murray after they both overcame big-serving opponents at the Australian Open.

Fifth seed Murray produced a near-flawless display to blunt the booming serve of 6ft 9in American John Isner and win 7-6 (7/4) 6-3 6-2.

Nadal had a similarly imposing task against Ivo Karlovic, who stands 6ft 10in, and while the Spaniard dropped a set he did enough to win 6-4 4-6 6-4 6-4.

The six-time grand slam winner has not always looked at his best at Melbourne Park and admitted it had been hard to find a flow in a match dominated by Karlovic’s reliance on his serve.

‘‘It is is probably one of the most difficult matches to play well because it is without rhythm all the time,’’ he said.

‘‘So the victory is the only thing in this kind of match, and I did that.

‘‘I think I returned aggressively and when I had a chance to get a racquet on the ball I did well.’’ Nadal’s win sets up a difficult quarter-final clash against Murray, who has yet to drop a set.

The Scot would also be encouraged by Nadal’s poor recent form against top-10 players – he has won just one of his past 11 meetings with the top bracket of players – while Murray memorably beat him en route to his only grand slam final at the 2008 US Open.

Despite the statistics, Nadal is optimistic, saying: ‘‘It is probably not the best form of my career against the top ten.

‘‘But I am happy with the draw. The most important thing is I am in the quarter-finals and I have only lost two sets.

‘‘Andy is definitely one of the more difficult players to play against. I know I will have to play my best tennis.’’ Murray admitted he was playing close to his best after he had another routine win.

The 22-year-old did have to fend off a set point in the first set, but after taking it in a tiebreak it was one-way traffic to send him into the last eight for the first time.

‘‘I’m playing well, no question about that,’’ said Murray, who made just eight unforced errors in just over two hours on court.

‘‘I just need to play like I have been and maybe a bit more if I want to win the tournament.

‘‘Today when I was down I hit a lot of winners, served smart, was just thinking the whole time.’’ Marin Cilic gained some revenge over fourth seed Juan Martin del Potro as he dumped the US Open champion out in five sets.

Cilic, the 14th seed, lost to Del Potro at this stage last year, while the Argentinian also knocked him out en route to his success at the US Open.

The 21-year-old Croatian fired 71 winners as well as 20 aces to win 5-7 6-4 7-5 5-7 6-3 in four hours and 38 minutes on Hisense Arena.

Cilic will play seventh seed Andy Roddick after he also went the distance in the late game against Fernando Gonzalez.

The American, who is a four-time semi-finalist at Melbourne Park, rode his luck on the review system with his successful challenge to clinch the fourth set a turning point in a match he won 6-3 3-6 4-6 7- 5 6-2 in three hours and 21 minutes.

‘‘I got a little lucky,’’ Roddick said. ‘‘Sometimes it’s better to be lucky than good.

‘‘I’ve lost in the semis four times so I hope to get at least one further than that.’’ Teenager Laura Robson moved into the quarter-finals of the women’s doubles as her new partnership with Australian Sally Peers continued to blossom.

The duo only decided to team up on the eve of the tournament and have now won all three games they have played after beating Vera Dushevina and Anastasia Rodionova 6-3 6-3.

Their next opponents will either be the third seeds Maria Jose Martinez Sanchez and Nuria Llagostera Vives or 14th seeds Maria Kirilenko and Agnieszka Radwanska, who play today.

Robson, who turned 16 on Thursday, will also play in the junior women’s draw with her opening game today.