By Julian Linden
MELBOURNE (Reuters) - The easy part is over for Andy Murray. The Australian Open is about to get a whole lot tougher for the great hope of British tennis.
Murray coasted through his first four matches without dropping a set but his quarter-final opponent in Tuesday's feature night match presents a much bigger challenge.
By his own incredible standards, Rafa Nadal is not at his best. The Spaniard has struggled with injuries since winning last year's Australian Open and is only just regaining his confidence.
There have been plenty of indicators to suggest he is getting back to his old form and his clash with Murray could be a watershed for both men.
"I think I am okay," Nadal said. "But I have to play better next match if I really want to have chances to win.
"Andy is one of the more difficult players to play against. I have to play my best tennis."
Nadal has won five of his previous seven meetings with Murray but the Scotsman is not without hope. Nadal has won just one of his last 11 matches against players ranked in the top 10.
"I'm happy to have won the matches comfortably. I know the match against Rafa is going to be difficult, but I think I can win."
The winner of that match will advance to the semi-finals against either American Andy Roddick or Croatia's Marin Cilic.
Their match, also scheduled for Tuesday, is shaping as a battle of the fittest after both were pushed all the way in their fourth round encounters.
Cilic upset Argentina's U.S. Open champion Juan Martin del Potro in five sets while Roddick also went the full distance before wearing down Chile's Fernando Gonzalez.
Roddick and Cilic have played each other twice before, winning one apiece, but the American said those matches would have no bearing on their next clash.
"I don't think we can put much stock into our previous meetings," Roddick said.
"I remember I played him at Queen's a long time ago, he played pretty badly. Then I played him in Canada, and I played pretty badly."
Justine Henin's comeback to professional tennis is building momentum but she faces a tricky quarter-final against Russia's Nadia Petrova, the only seed left in the bottom half of the women's draw.
Petrova made it through to the last eight with back-to-back wins over U.S. Open champion Kim Clijsters and French Open champion Svetlana Kuznetsova and is in the best form of her career but it remains to be seen how seasoned Henin is.
"It's only my second tournament (back)," she said.
"Of course, I have dreams. I'll try to go as far as possible. If it's till the end, it would be amazing but it's still too early to talk about that."
Zheng made the semi-finals at Wimbledon two years ago while Kirilenko, like Petrova, has been something of a giantkiller, beating both Maria Sharapova and Dinara Safina on her way to the quarters.
(Editing by Patrick Johnston)