(Reuters) - Built Belgian tough might become a badge of honor for future tennis generations after courageous Kim Clijsters' win over Li Na Sunday, while Roger Federer dashed the dreams of home fans by crushing young gun Bernard Tomic.

On a day when the clouds cleared, the mercury bubbled and temperatures soared, Rafa Nadal won a battle of Spanish lefties against Davis Cup team mate Feliciano Lopez, and Tomas Berdych was booed mercilessly for a petulant show of bad sportsmanship.

Defending champion Clijsters crumpled to the court at 3-3 in the first set after her left ankle rolled sickeningly over.

The Belgian, bidding farewell to the Australian Open in the final year of her career, had her ankle heavily strapped and Li took advantage to win the first set.

The 28-year-old Belgian clawed her way back into the match to win the second set in a tiebreak as the crowd began to believe she could pull off the win. Clijsters closed out the match 4-6 7-6 6-4 to keep her hopes alive of a fifth grand slam title.

However, she conceded the injury had made her think about quitting against Li, whom she beat in the 2011 final.

It definitely crossed my mind at some point, but I knew if I could just try to let the medication sink in ... the pain would go away a little bit and maybe with the adrenaline I could just fly through it, she said.


Clijsters was joined in the quarter-finals by number three seed Victoria Azarenka, who endured her traditional late-game hiccup before beating Iveta Benesova 6-2 6-2.

World number one Caroline Wozniacki endured a nervy second set against Jelena Jankovic before clinching a 6-0 7-5 win.

Still giddy from Lleyton Hewitt's heroics against Milos Raonic, Australian fans could barely believe they had two players in the men's fourth round, but hopes that 19-year-old Tomic could depose four-times champion Federer proved wide of the mark.

Teen Tomic had already come through two five-setters to reach the fourth round while 30-year-old Federer looked as fresh as a daisy in securing a 6-4 6-2 6-2 win.

The Swiss, bidding to match Roy Emerson's record of five Australian Open titles, will face former U.S. Open champion Juan Martin Del Potro in the quarter-finals.

Federer agreed Tomic had the potential to win silverware.

I think he has had a wonderful tournament and there's much more that's going to come the Australian way, he said.

It's going to be tough against Del Potro. I don't look beyond that because he's coming up strong. He has had a good year, played all the top guys again and pushed us all.


World number two Nadal, with heavy strapping on knee, ankle and foot, huffed and puffed his way past Lopez with little Spanish sparkle but was happy to go no more than three sets.

Memories of his last eight withdrawal against Andy Murray two years ago, and defeat at the hands of David Ferrer last year, still haunt him.

Hopefully it won't happen this time, said Nadal after his 6-4 6-4 6-2 win. Every year is different. I had a bad experience for the last two years here. It's tough to have to go out of a tournament like Australia in quarter-finals.

In the day's only real note of controversy, Czech Berdych was booed off Hisense Arena after a bad tempered 4-6 7-6 7-6 7-6 win over Nicolas Almagro.

Berdych refused to shake hands with the Spaniard after he sealed the win because he felt the 10th-seeded Almagro had deliberately blasted a return at his head during the fourth set.

The court is pretty big and you always have some space to put the ball in, number seven Berdych complained. And not even if you are standing three or four meters from the guy (does he need) to hit it straight to your face.

This is not the way how tennis is.

Berdych's courtside interview was drowned out by the crowd booing and hissing, while tennis coach and commentator Brad Gilbert said he was appalled at the Czech's decision.