It will be Australia versus the world No.1s on a blockbuster Monday on Rod Laver Arena.
The start of the second week of the Australian Open traditionally brings out the big guns of world tennis - and this year's feast is no exception.
Australia's two remaining hopes in the singles, Lleyton Hewitt and Samantha Stosur, face monumental tasks to qualify for the quarter-finals as they take on tennis's king and queen Roger Federer and Serena Williams.
Hewitt, the world No.22, won seven of their first nine encounters but has lost the past 14 matches against the Swiss maestro, a streak stretching back to his famous five-set comeback win in a Davis Cup semi-final seven years ago.
The 28-year-old has never beaten Federer in seven previous Grand Slam meetings, including a four-set loss in their only clash at the Australian Open in 2004.
Hewitt, however, remains confident of causing an upset.
"He doesn't lose too many matches, especially big matches, and especially Grand Slams. You've just got to look at his record (26-2) last year in Grand Slams," Hewitt said.
"Yeah, it does take a great performance to beat him. That's why he's been the greatest player possibly ever."
"But you play for those moments, to play against the best players - Roger is that. This is what motivates you. If you can't get up for these matches, you shouldn't be playing the game."
Hewitt could not be happier with his form leading into this much-anticipated match, after pounding old rival Marcos Baghdatis 6-0 4-2 before the Cypriot retired with a shoulder injury in their third-round match two days ago.
"I didn't put a foot wrong," Hewitt said.
"I served great. I moved great. I hit the ball fantastic. I did all the right things on my side of the court."
"I took care of my service games extremely well and was confident and put a lot of pressure on him."
Stosur takes a more encouraging record into her match with Williams, having beaten the American the last time they met in the quarter-finals at Stanford last July and also holding match points in one of her losses.
After a slow start to the year, Stosur has slowly gathered momentum - and Williams holds no fear for the world No.13.
"I'm going to have to stand my ground, stand up to her and give her my best shot," said Stosur.
"I'm looking forward to it. I've lived up to my expectation. Now, playing the No.1 player in the world, the defending champion, I can go out there and really enjoy it."
Added Williams: "She beat me the last time we played, so she has a lot of momentum. A ton of momentum. She's serving incredibly well and moving even better. She has nothing to lose going into this match, but neither do I."
A victory to the 11-time Grand Slam winner would keep hopes of an all-Williams semi-final alive.
Older sister Venus opens proceedings on Rod Laver Arena on Monday against 17th seed Francesca Schiavone.
The No.6 seed knocked out Australian wildcard Casey Dellacqua in the third round but will have to step up her game against the in-form Italian, who thrashed Poland's Agnieszka Radwanska 6-2 6-2.
That match will be followed by what looks like being another epic, as Spanish ninth seed Fernando Verdasco takes on No.6 Nikolay Davydenko.
The Russian is arguably the form player on tour at the moment and