Novak Djokovic's Australian Open title hopes will come under close scrutiny when the defending champion takes on Stanislas Wawrinka on Tuesday.
Djokovic has barely broken a sweat in his progress to the last eight, with the world No 2 having brushed aside Lukas Lacko, Leonardo Mayer, Denis Istomin and Fabio Fognini in straight sets.
However he will face his first top 10-ranked opponent so far at the tournament in the shape of eighth-seeded Wawrinka.
The 28-year-old from Switzerland has had a fairly straight-forward route into the quarter-finals of his own, aided by Andrey Golubev's withdrawal midway through their first round clash and 28th seed Vasek Pospisil handing him a walkover win in the third round due to a back problem.
Alejandro Falla did take Wawrinka to four sets, but 17th seed Tommy Robredo was seen off 6-3 7-6 7-6 to set up the Djokovic clash.
Despite the step up in class of opponent, Djokovic will still be the favourite to advance to the last four - especially as he has a 15-2 winning record over Wawrinka, including victories in the last 14 encounters.
Wawrinka, though, certainly made life hard for the Serbian at last year's Australian Open before finally losing that fourth-round clash 1-6 7-5 6-4 6-7 (7-5) 12-10.
The second quarter-final is expecting to be an equally close affair, with No 3 seed David Ferrer taking on seventh-ranked Tomas Berdych.
Ferrer has won seven of the 11 meetings between the two rivals, although Berdych was a 6-4 6-4 winner in their last clash at the ATP World Tour Finals in London.
Like Djokovic, Berdych is yet to drop a set in Melbourne this year - with the Czech losing just 33 games in his four matches.
Ferrer, though, has been taken to four sets by Florian Mayer and Adrian Mannarino.
In the women's quarter-finals Ana Ivanovic will look to build on her shock victory over Serena Williams when she faces Eugenie Bouchard.
On paper 14th seed Ivanovic should have few problems against the Canadian teenager, however Bouchard did win their only previous encounter - a 6-3 6-3 success at last year's Wimbledon.
Ivanovic has come through two tough three-setters to reach the last eight as well, although she will be the first seed Bouchard has faced so far.
Na Li, last year's beaten finalist, also has a tough match in store - with the fourth seed up against Flavia Pennetta.
This will be the fifth meeting between the two 31-year-olds, with two wins apiece so far. No 29 seed Pennetta, who ousted Angelique Kerber en route to the quarters, was victorious last time out, though, with a 6-2 7-5 win at the Sydney International in 2010.