|Wozniacki beat Latvia's Anastasija Sevastova to reach the quarter-finals at Melbourne Park [GALLO/GETTY]
Women's world number one Caroline Wozniacki recruited a fictional kangaroo to explain an injury following her successful bid to reach the Australian Open quarter-finals, while Stanislas Wawrinka outclassed eighth seed Andy Roddick 6-3 6-4 6-4 to set up a match with close friend and fellow Swiss Roger Federer.
Wawrinka out-aced American Roddick 24-9 as he ensured a first Grand Slam quarter-final between two Swiss men since the sport turned professional.
Federer earlier toiled in the sun for a 6-3 3-6 6-3 6-2 victory over Spain's Tommy Robredo.
Wawrinka, seeded 19th, caught Roddick cold under the Melbourne floodlights, breaking for 5-3 in the first set with a drilled backhand pass and never looked back.
Roddick was a step slower than his opponent, who had too many ideas and executed his shots superbly.
The contest ended after two hours and 22 minutes when Roddick sliced a weary backhand into the net to leave no Americans remaining in either singles draw.
Wozniacki continued her news conference shenanigans, telling a tale of being scratched by a kangaroo and then later admitting on social networking website Twitter she had made up the story.
After making the quarter-finals with a 6-3 6-4 victory over Latvia's Anastasija Sevastova, the Danish world number one told reporters she was attacked by a baby kangaroo at a wildlife park outside Melbourne and had needed to get medical attention.
"I thought I was going to be nice and try to help it out because it was just lying there. I thought maybe it needed some help... I found out that I shouldn't do that," said Wozniacki, after pointing to some tape covering a 'wound' on her leg.
|Roddick's defeat meant there were no Americans left in either singles draw [AFP]
"It looked so cute. But once it started scratching me, I was a coward and I ran away."
Wozniacki said on Twitter: "Round 2 with the media:) hope you enjoyed my kangaroo story, hope you know i was just kidding:) see you on tuesday for round 3!"
She later returned to the interview to apologise to the media.
"I'm sorry if I've caused any harm or made your job a little bit more difficult," she said.
"But the kangaroo story, I made it up because it sounded better than what actually happened. I walked into the treadmill."
Former world number one Maria Sharapova suffered a fourth round shock on Sunday when she was bundled out 6-2 6-3 by Germany's Andrea Petkovic.
On the back foot from the start, Sharapova committed 30 unforced errors in a performance which underlined her struggles since her shoulder surgery in late 2008, the year she won the title in Melbourne.
Fourteenth seed Sharapova, a three-times Grand Slam champion, made a late charge from 2-0 down in the second set, saving two match points with a pair of rocket forehands.
But the Russian had dug herself too big a hole against a dangerous opponent and Petkovic completed victory in 79 minutes with a deep serve Sharapova could only push into the net.
Bosnian-born Petkovic celebrated reaching the last eight of a major for the first time with an on-court jig.
"It started off as a bet with my coach," Petkovic told reporters of the dance of delight she peformed after her upset win.
"I'm very superstitious and since I started doing the dance I'm playing much better, so I'll try to keep it up," added the 23-year-old, who faces China's Li Na in the quarter-finals.
Novak Djokovic steamed into the last eight with a 6-3 6-4 6-0 thrashing of Spaniard Nicolas Almagro on Sunday but fumed after being given a code violation for coaching during the match.
Djokovic was sanctioned by chair umpire Fergus Murphy early in the second set, but said he had only made eye contact with coach Marian Vajda in the stands.
"I don't think it was the right call, because I missed a forehand and then I turned to my coach as you always make as a player an eye contact with your team," said the world number three Djokovic, who faces a possible fine following a review.
"That's what I did. I didn't ask for any advice, you know, because they can't help too much. You've got to do what you got to do."