Rafa Nadal fought back to topple great rival Roger Federer 6-7 6-2 7-6 6-4 in an enthralling Australian Open semi-final of the highest quality on Thursday.

Rafal
Rafal Nadal celebrates after beating Roger Federer at the Australian Open 2012.

Like so many of their battles over the years, the 27th meeting was a feast of shot-making, with exhilaration and suspense served up in equal measure under the lights of a packed Rod Laver Arena.

Amid an atmosphere more akin to a football match, Nadal's brute force triumphed over the Swiss's artistry as he captured the decisive break at 4-4 in the fourth set and closed it out on the second match point when Federer blasted a forehand long.

With raucous cheers ringing from the stands, the Spaniard slid out on to the blue centre court on his knees and leaned back to gaze at the night sky.

It's always a pleasure being on this court, the world number two said in a courtside interview after setting up a final against top seed Novak Djokovic or Andy Murray.

It's an honour to play Roger. It was a fantastic match.

It's just amazing to have one player in front of you who has no mistakes and a totally complete game.

Third seed Federer, just shaded on a night of high drama, had his chances to overhaul the Spaniard in the tension-charged fourth set but missed a break point when leading 4-3 and another two as Nadal served out the match.

The loss was Federer's second to Nadal on Rod Laver Arena, where he wept bitter tears after losing a five-set classic for the 2009 title.

It also extended his losing record against Nadal to 18-9, with eight defeats in their 10 grand slam matches, a rivalry only matched in the majors by John McEnroe and Ivan Lendl in the 1980s.

Victoria Azarenka and Maria Sharapova Scream to Victory

Grunt work saw Victoria Azarenka and Maria Sharapova reach the Melbourne Park final on Thursday, as Roger Federer and Rafa Nadal prepare for a mouthwatering semi-final that could leave fans shouting from the rooftops on Australia Day.

Tears stung the cheeks of Azarenka after an emotional 6-4 1-6 6-3 victory over defending champion Kim Clijsters earned the world number three her first grand slam final place.

The 22-year-old came out on top of a bruising baseline battle in the first set, dragging Clijsters from side to side before putting away forehand winners deep in the corners for dream start to just her second grand slam semi-final.

The second set was more akin to a nightmare for the pony-tailed righthander, who got just 35 percent of her first serves in and made 16 unforced errors.

Azarenka, who has been at the mercy of her emotions throughout her career, showed impressive composure to gather herself and put Clijsters on the back foot in the third set, wrapping up the semi-final in two hours, 12 minutes.

A Wimbledon semi-finalist last year, Azarenka told the crowd her temper tantrums were a thing of the past.

I think before you all thought that I was a mental case, the 22-year-old said in a court-side interview. I was just young and emotional.

Azarenka admitted she had struggled to keep it together in the final moments of the third set.

I felt like my hand is about 200kg and my body is about 1,000 and everything is shaking, said the Belarusian, emotion etched over her face. But that feeling when you finally win is such a relief, it's like 'My God! I cannot believe it's finally over', I just want to cry, she added.

Azarenka will be the first player from Belarus to contest a grand slam final since 1988 when Natasha Zvereva lost 6-0 6-0 to Steffi Graf at the French Open.

BUILT BELGIAN TOUGH

Clijsters is thought to be in her last season on Tour but the 28-year-old has shown the kind of physical and mental toughness that would stand her in good stead for years to come.

A back-from-the-brink victory over Li Na in the fourth round in which she suffered a nasty ankle injury served to bolster her aura of invincibility at Melbourne Park.

However, there would be no storybook finish for the player affectionately known as Aussie Kim, though she certainly did not feel she had anything left to prove.

I know I'm capable of beating all these girls, but it's whoever is better on the day wins and gets to go through, she added.

Fourth seed Sharapova overcame a second set rally by Petra Kvitova to advance to her third Australian Open final with a 6-2 3-6 6-4 victory, though she never quite reached top form.

The victory was sweet revenge for Sharapova, who had lost to the Czech in last year's Wimbledon final.

I love this sport and sometimes even if you're not playing your best tennis, you can find a way to win, she said.