Roger Federer survived a withering challenge from Frenchman Jo-Wilfried Tsonga to prevail 7-6 4-6 7-6 3-6 6-3 in Rod Laver Arena and reach the Australian Open semi-finals on Wednesday.

Seventh seed Tsonga unleashed a barrage of brilliant shot-making to level the match at two sets apiece but the Swiss maestro was composure personified as he captured the decisive break at 2-1 in the fifth.

Battling for survival, Tsonga saved four match points when serving to stay in the match, but Federer closed out victory on the fifth with an overhead smash to reach his 10th straight semi-final at Melbourne Park.

"It was a tough close for sure, but the whole match was tough. Any set could have gone any way," the 31-year-old said in a courtside interview.

"I feel a bit lucky obviously to come through... but it was great pleasure to play Jo because he played great too"

Roger Federer

"I feel a bit lucky obviously to come through... but it was great pleasure to play Jo because he played great too.

"We haven't played for a year... but I thought he played extremely aggressive."

Federer, seeded second, will play third seed Andy Murray for a place in the final as he continues his bid for a fifth title at Melbourne Park.

"I'm young, you know, I'll recover quick - compared to the seniors, of course," Federer joked.

"I'm looking forward to it. He's a great guy, a great player."

Earlier the great shock of the day was the exit of Serena Williams. 

American teen Sloane Stephens went to bed on Tuesday wondering if she had the game to topple her idol in the Australian Open quarter-finals, but after beating the five-times Melbourne Park champion in three sets she said it wasn't as hard as she thought.

After a tentative start, the 19-year-old went toe-to-toe with an injury-hampered Williams on Rod Laver Arena on Wednesday to claim a 3-6 7-5 6-4 win and set up a semi-final with defending champion Victoria Azarenka.

Hailed as the future of American tennis, Stephens said she needed time to convince herself she could send 31-year-old Williams packing from the first grand slam of the year.

"Last night I was thinking about it and... someone asked me like, 'Do you think you can win?' I was like, 'Yeah, I think so', but I wasn't too clear about it," Stephens told reporters after pulling off the biggest upset of this year's tournament.

"Then this morning when I got up, I was, 'Look, dude, you can do this. Go out and play and do your best.'"

Men's semi-final draw:

Thursday 
Novak Djokovic v David Ferrer

Friday
Andy Murray v Roger Federer

Women's semi-final draw:

Thursday
Victoria Azarenka v Sloane Stephens
Li Na v Maria Sharapova  

Source: Agencies