Serbian Ana Ivanovic has pulled off the upset of the Australian Open so far with defeat of top seed and overwhelming tournament favourite Serena Williams.
Ivanovic, the 14th seed, won their fourth-round match 4-6 6-3 6-3 at Melbourne Park on Sunday.
The 2008 French Open champion hadn't won a set against Williams in their four previous meetings but she troubled a lethargic world No.1 from the opening game.
"It's not easy playing such a champion," Ivanovic said.
"But she is just human."
Ivanovic will face either Australian Casey Dellacqua or Canadian 30th seed Eugenie Bouchard in the quarter-finals.
Ivanovic joins two-time Australian Open finalist Li Na in the quarter-finals after the Chinese star scored a dominant fourth-round victory over Russia's Ekaterina Makarova.
The fourth-seeded Li took less than an hour to dispose of Makarova 6-2 6-0, setting up a quarter-final against Italy's Flavia Pennetta.
Li has led in both her finals in Melbourne - against Kim Clijsters in 2011 and Victoria Azarenka last year when severely hampered by an ankle injury.
Pennetta, the 28th seed, endured more serious opposition from German ninth seed Angelique Kerber before registering one of her best grand slam wins 6-1 4-6 7-5.
Despite being closer to the end of her career than the beginning, Pennetta's run is her best in 10 appearances at the Australian Open and follows her best-ever grand-slam performance when a semi-finalist at last year's US Open.
Li broke Makarova in the third game of the opening set, establishing a superiority that was barely threatened.
A second break gave Li a 5-2 lead and she duly served out for a 1-0 lead.
The only lapse in Li's performance came in the fourth game of the second set when she offered her opponent two break points which she failed to convert.