Easy for Novak at injury-hit Open

 Novak Djokovic had time for jokes and smiles as he knocked over a hobbling Nicolas Mahut at the injury-hit Australian Open today -- but there were tears as two top women lost out.

As a furious David Nalbandian vowed to fight his 'Watergate' fine, Djokovic did his best to cheer up struggling Mahut on his 30th birthday by happily playing to the crowd as he dispatched the Frenchman 6-0, 6-1, 6-1.

Mahut, compromised by a left knee injury, maintained his good humour and he shrugged and smiled broadly to fans as he finally won his first game at the start of the second set. He was later given a birthday cake by reporters.

"Credit to Nicolas. Obviously, he had some strapping around his knee and I felt sorry for him," said defending champion and top seed Djokovic, who remains on course for a semi-final with Andy Murray.

"Evidently he was not moving well, he was not able to perform his best, but he didn't want to retire and he wanted to stay all the way so I wish him happy birthday."

Mahut, who lost the longest match in tennis history at Wimbledon 2010, was not the only injury casualty on day six as Russia's Maria Kirilenko became the second women's retirement in quick succession.

Just hours after Anabel Medina Garrigues agonisingly rolled her ankle against Li Na late on Friday, Kirilenko lasted until just game two of the second set against Petra Kvitova before retiring with a thigh problem.

Wimbledon champion Kvitova took another step towards seizing the world number one ranking from Caroline Wozniacki, setting up a round four match with Serbia's Ana Ivanovic, who won in straight sets against Vania King.