LEAD: Nadal, Federer roll efficiently into the fourth round

By Bill Scott Jan 20, 2012, 5:45 GMT

Melbourne - Former champions Rafael Nadal and Roger Federer earned an all-star double Friday as both rolled into the fourth round of the Australian Open with straight-set success.

Nadal, the 2009 champion, picked up the pace after starting the Australian Open with a knee injury scare with the Spaniard defeating qualifier Lukas Lacko 6-2, 6-4, 6-2.

Federer, a four-time winner at Melbourne Park, overcame Ivo Karlovic 7-6 (8-6), 7-5, 6-3, saving a set point in the first set with a winning lob over the head and outstretched racquet of the 2.08-metre Croatian.

The Swiss third seed won his 10th match of 11 meetings with Karolvic, who was held to a modest 15 aces in the contest lasting two and a quarter hours.

'I knew it would be tough, but maybe I played the percentages slightly better and had some luck,' the Swiss national said. 'I played better as the match went on.'

Nadal's victory lasted just under two hours as the Spaniard put more distance between himself and the shoulder and knee problems that have concerned him over the past few months.

'The knee is fine; that's the important thing,' Nadal said. '... Being in the fourth round without losing a set, it's fantastic news.'

He booked into a weekend meeting with the winner of the match between fellow Spaniard Feliciano Lopez and 16th-seeded American John Isner.

'I've played three matches at a very good level,' said the player searching for his first title since last year's French Open. 'Today was one of the best - solid, without mistakes. I was comfortable with the serve and had good returns.'

Women's top seed and world number one Caroline Wozniacki posted a win over Monica Niculescu of Romania 6-2, 6-2.

'I felt like it was up to me what was going to happen out there on court,' Wozniacki said.

Third seed Victoria Azarenka let her temper flare after late-match line calls that she thought were wrong.

But the Belarus player who won Sydney last weekend held on for a 6-2, 6-4 defeat of German Mona Barthel, winner of the Hobart title this month in Australia from a qualifying start.

Azarenka got overheated after expecting a line call out on one point and was further incensed when a shot from her opponent appeared to land wide but was called good.

Azarenka would have challenged the call, save the fact that she had used up her match quota. She took out her frustrations on a line judge on the way to victory.

'I needed something to get my emotions going to finish the match because I had a few chances and I didn't convert them,' the winner said. 'Sometimes, you just have to push yourself a little bit to get going again.'

Polish number eight Agnieszka Radwanska advanced over Galina Voskoboeva 6-2, 6-2, Germany's Julia Goerges defeated Italo-Swiss Romina Oprandi 3-6, 6-3, 6-1 and Czech Iveta Benesova beat Russian Nina Bratchikova for a fourth-round spot 6-1, 6-3.