Tennis: Tough first week sets Federer up for business end of draw

The Swiss beat Tommy Robredo and, while it was always a match he was going to win, the way his concentration disappeared in the second set displayed an element of vulnerability and raised more questions as to whether the world number two can defend the title he won 12 months ago.

He eventually prevailed 6-3 4-6 6-3 6-2 but admitted he had been subjected to a "tough" opening week.

"I'm satisfied I'm still in the tournament." he said. "I'm in another quarter-final and have a good chance to make it to the semis again, so I'm very pleased.

"It's been a tough first week with a bit of heat the last couple of matches I played in."

Federer will meet countryman Stan Wawrinka next after he crushed Andy Roddick 6-3 6-4 6-4 with a wonderful display.

Third seed Novak Djokovic advanced with a hugely impressive win against Nicolas Almagro.

The Serbian, the champion here in 2008, withstood everything the big-hitting Spaniard could throw at him before sprinting through the third set to complete a 6-3 6-4 6-0 victory.

Djokovic has flown under the radar so far in Melbourne with all the focus falling on Nadal and Federer and, although his displays in the previous rounds would not have unduly worried the big two, the third seed found his range.

"I'm happy and feeling good energy-wise. I didn't spend that much time on the court in the opening week," said Djokovic.

On Saturday, Andy Murray impressed when he advanced to the last 16 with a comfortable 6-1 6-1 6-2 victory over Guillermo Garcia-Lopez in just one hour and 22 minutes.

That set up a clash with 11th seed Jurgen Melzer, from Austria, which was taking place in the early hours of this morning.

In the women's draw, Francesca Schiavone moved into the last eight after edging out Svetlana Kuznetsova in the longest women's grand slam match in the open era.

The Italian saved six match points along the way as she triumphed 6-4 1-6 16-14 in four hours and 44 minutes.

World No 1 Caroline Wozniacki joined her in the quarter-finals with a scrappy victory over Anastasija Sevastova.

The Dane, who is chasing her first grand slam title, was functional rather than impressive but still possessed too much for Latvian Sevastova, winning 6-3 6-4 in one hour and 20 minutes.

"Sometimes you just need to get through that period where you don't feel like you're playing your best tennis," said Wozniacki. "I think that the real champions come through even though they're not playing at their highest level."