"It was a really complete match, a really solid one. I'm very happy about my game," said Nadal, who has made untroubled progress into the last 16.

"Being in the fourth round without losing a set, it's fantastic news."

Lacko looked Nadal's equal in the opening exchanges, trading blows with the 10-time Grand Slam champion, but he could not maintain it and Nadal took full advantage to cruise through.

The world number 119 dropped his serve in the opening game but then hit back with some powerful shots to level the scores.

But once Nadal seized Lacko's serve to establish a 3-2 advantage and then broke again for 5-2, the tone for the rest of the match had been set.

An early break in the second set maintained Nadal's momentum and two more in the third wrapped up what ultimately was a routine win for the Spaniard.

"I am playing well and if you are playing well, things can be a little bit less difficult," Nadal said.

"If you are playing bad, every match will be very, very difficult.

"I have done well, played all three matches at a very good level. Today was one of the best, solid, without mistakes, comfortable with the serve, having good returns.

"I played solid all match."

Roger Federer followed Nadal onto Rod Laver Arena and promptly followed him into round four, although he too was made to work hard by giant Croatian Ivo Karlovic before sealing a 7-6 (8/6) 7-5 6-3 success.

Karlovic, at 6ft 10in, posed the Swiss the usual conundrum of how to break his formidable serve.

And for almost two sets, Federer failed to find the answer.

Indeed, having taken the first set to a tie-break, Karlovic set up a set point at 6-5 only for the world number three to produce a bit of magic to reach a mis-hit volley, which just dropped over the net, and clip a clever lob over his towering opponent.

A wonderful backhand return then handed Federer a set point of his own and he made no mistake to edge in front.

Karlovic threatened again at 1-1 in the second on break point but Federer served his way out of danger.

It took Federer, the winner of a record 16 grand slam titles, until the 25th game of the match to create a break point of his own, and when he did it was a set point.

Karlovic saved the first but there was no denying Federer second time around as a Karlovic volley under pressure drifted long.

It looked a long road back for the Croatian and although he saved three break points at 0-1 in the third, he could not repeat the feat when Federer threatened again at 1-2.

He duly served it out to move through to face the winner of tonight's clash between Bernard Tomic and Alexandr Dolgopolov.

"He is so tall and makes it unusual," Federer said of Karlovic. "It was always going to be tough and you need a bit of luck. I got fortunate and started to play better as the match went on."