Wozniacki battles through

Down a set and trailing 3-1, the Danish top seed shifted up a gear to mow through six straight games before closing out a hard-fought match in 144 minutes under a cloudy sky at Rod Laver Arena.

The 30-year-old Schiavone saved three match points and broke Wozniacki to claw back to 5-3 in the third, but her record-breaking marathon against Svetlana Kuznetsova showed as she tired to surrender the match in a hail of unforced errors.

"I definitely had to step it up a little bit today," said world number one Wozniacki, who will play China's Li Na for a place in the final, after the ninth seed dismissed Germany's Andrea Petkovic 6-2 6-4.

"I was going for some shots that maybe weren't the smartest. Then she went in and played aggressive at important points.

"In the end I figured out how to play. I stood a little bit closer but still was placing the ball well and made her run a lot. That's what gave me the good result in the end."

The blonde 20-year-old will be glad to have finished off strongly after appearing listless and leaden-footed for half of a match that pitted the oldest player left in the draw with the youngest.

She managed only a single winner in the first set, while evergreen hustler Schiavone had a swipe at everything, determined to wrap proceedings up quickly after being involved in a four-hour and 44-minute war of attrition against Russian Kuznetsova, a women's Grand Slam record.

The feisty French Open champion's fast start was rewarded with a breakpoint at 4-3, and the out-of-sorts Wozniacki defended it weakly, poking a half-hearted forehand into the net.

Schiavone survived three of her own break points in the next game then wrapped up the set with a fearless rush to the net to guide a sweetly-struck backhand volley down the line.

Wozniacki took a lengthy medical time-out between sets to have a leg strain treated and fussed with bandages on the area as she lost her serve again, courtesy of a cruel deflection off the net that left her swiping at air.

"I think it's... I don't know if it's the hip flexor. It's on the side of leg anyway," said Wozniacki. "I felt it when I was serving and I fell down on my leg.

"First the tape was too restricting and too tight. I got some painkillers that helped me, and after 15, 20 minutes I didn't feel it."

The match turned on its head at 3-2 in the second set, as Schiavone appeared to suffer a brain-freeze, blasting a clutch of wayward shots to surrender her serve.

Wozniacki sensed her chance and began dictating the play, bashing winners off the baseline and moving the tiring Schiavone around the court.

Schiavone pushed a languid return down the tram-lines to concede the set and botched an easy volley in the next game to go a break down in the third.

The Italian scrapped her way back but Wozniacki slammed the door shut with a deft lob that left Schiavone stranded at the net and trailing 5-2.

Sixth seed Schiavone's quarter-final appearance will lift her ranking to four when the new lists come out next week, the highest ever for an Italian woman.

Wozniacki's semi-final appearance is her first at Melbourne Park after only making it as far as the fourth round in previous campaigns and ensures she will keep her top ranking.

The Dane brought a yellow, inflatable kangaroo into the post-match press conference, given to her by local media after she apologised for concocting a story about being scratched by a joey in a visit to a park outside of Melbourne.

There was little levity when she was asked about Li, who is on a 10-match winning streak and beat her easily in the quarter-finals of last year's tournament.

"I think Li Na has improved a lot, but I also believe I have," she said. "I know that she can play very good tennis, but I can too. It's just a matter of who wins the most important points in that match."