MELBOURNE  - US tennis queen Serena Williams crashed to one of the worst defeats of her glittering grand slam career Monday, as Novak Djokovic and Andy Murray moved safely into the Australian Open quarter-finals.
Williams, winner of 13 major titles including five in Melbourne, fell to the lowliest of opponents on the sun-baked centre court in Russia's Ekaterina Makarova, the world number 56 coming off a five-month losing streak. But 30-year-old Williams, who injured her right ankle this month, was far from her best in the error-strewn, 6-2, 6-3 defeat and she admitted afterwards that she wouldn't have played if the tournament was not a grand slam.
"My lefty serve is actually better than that. Maybe I should have started serving lefty," said Williams, who dished up seven double-faults and 37 unforced errors. "It was just disastrous really." The 2003, 2005, 2007, 2009 and 2010 winner, who missed last year's event with injury, has not suffered a similar grand slam defeat since 2005, when she lost to 85th-ranked Jill Craybas at Wimbledon.
Makarova, 23, whose victory stripped the competition of its last American singles player, is now into her first grand slam quarter-final -- after failing to get beyond a tournament first round since last August. "It's an amazing feeling, it's unbelievable," Makarova said. "She's an unbelievable player and I'm just really happy."
Williams's exit blows a giant hole in the women's competition with Makarova, her next opponent Maria Sharapova, and Wimbledon winner Petra Kvitova the potential beneficiaries on her side of the draw.
Sharapova beat Germany's Sabine Lisicki and Kvitova overpowered Ana Ivanovic to reach the quarter-finals, where she will meet Italy's Sara Errani. In the men's draw, defending champion Djokovic dropped his first set of the tournament against tireless Australian veteran Lleyton Hewitt before passing the late-night test 6-1, 6-3, 4-6, 6-3.
"I have give credit to Lleyton, who never gives up," said Djokovic. "He's a great competitor and he obviously made me play an extra shot and I made a couple of unforced errors." But Murray, who remains on course to meet Djokovic in the semi-finals, took the easy route to the last eight when Kazakhstan's Mikhail Kukushkin retired injured with the scores at 6-1, 6-1, 1-0.
"It's so hot on the court," said Murray, who played in the lunchtime heat. "It's obviously good for me that I got to conserve a bit of energy. It's tough for him -- it's his first fourth round in a slam, and he's obviously struggling." Murray's next opponent is Kei Nishikori, who became the first Japanese man in 80 years to reach the Australia quarter-finals when he shocked 2008 finalist Jo-Wilfried Tsonga in five sets. Djokovic now plays Spain's David Ferrer after the fifth seed beat Frenchman Richard Gasquet in straight sets. Kvitova reached the quarter-finals with a 6-2, 7-6 (7/2) win over Ivanovic -- but not before a temporary meltdown in which she embarrassingly swung and missed a simple overhead.
The cringe-making mistake late in the second set precipitated a brief nosedive and a flurry of errors but tough Kvitova steadied herself to seize control of the tiebreak. "I don't know if it's the worst (shot) in my career. It happened, I don't care really about it," she said. Elsewhere on day eight, China's Zheng Jie was beaten 6-2, 6-1 by Italy's Errani to end her country's singles interest on Chinese new year's day, and a day after Li Na's tearful defeat to Kim Clijsters.
And women's legend Martina Navratilova Monday said players were underpaid at the biggest tournaments, reigniting a debate that prompted rumours of a strike on the eve of the Australian Open. "I think the grand slams are making a lot more than they're sharing with the players. I think that's a fact," Navratilova said.

Men's singles 4th round results

Andy Murray bt Mikhail Kukushkin     6-1, 6-1, 1-0 -
Kei Nishikori bt Jo-Wilfried Tsonga     2-6, 6-2, 6-1, 3-6, 6-3
David Ferrer bt Richard Gasquet     6-4, 6-4, 6-1
Novak Djokovic bt Lleyton Hewitt     6-1, 6-3, 4-6, 6-3

Women's singles 4th round results

Petra Kvitova bt Ana Ivanovic    6-2, 7-6 (7/2)
Sara Errani bt Zheng Jie    6-2, 6-1
Ekaterina Makarova bt Serena Williams    6-2, 6-3
Maria Sharapova bt Sabine Lisicki    3-6, 6-2, 6-3.