Australian Open: Roger Federer glides into semi-finals

The fourth seed was in commanding form througout and wasted little time in despatching of his Argentinian opponent, who struggled to get to grips with Federer’s slick, clinical groundstrokes.

Federer now could meet Rafael Nadal for the first time in a Grand Slam semi-final, providing the Spaniard can overcome Tomas Berdych in the day’s later match.

Federer only lost his serve once in an efficient display. He held a 4-1 lead in the first set but Del Potro broke back to make it 4-4. However, Federer broke the former US Open champion to clinch the set 6-4 and from that moment on, he never looked back.

A solitary break in the second set gave him the platform to win it 6-3, although Del Potro did hold two break points when Federer looked to serve it out. The third set was a more serene affair for the Swiss, a double break allowing him to clinch it 6-2.

Kim Clijsters kept her Australian Open title defence on track today by moving into the semi-finals with victory over Caroline Wozniacki – stripping the Dane of her number one ranking in the process.

Showing no signs of the ankle injury sustained in her thrilling fourth-round win over Li Na – a match in which she had to save four match points – the Belgian had too much know-how for Wozniacki, whose search for a maiden grand slam title goes on.

It looked plain sailing for a rampant Clijsters as she raced into a set and 5-2 lead only for Wozniacki to launch an impressive fightback.

But it proved in vain, Clijsters’ greater experience shining through as she clinched a 6-3, 7-6 (7/4) win and a last-four spot against Victoria Azarenka.

“It definitely didn’t feel like I was up a set and 5-2, Caroline is a very consistent player and a fighter and she became more aggressive,” said Clijsters.

“I am happy to get through and not have to go to a three-setter as it’s so hot.”

The result will add weight to the argument of those who believe Wozniacki was not worthy of top spot, with the legendary Martina Navratilova yesterday demanding the WTA overhaul the current rankings system.

The 22-year-old has been at the summit for 67 of the past 68 weeks but the door now opens for Petra Kvitova, Azarenka and Maria Sharapova with the identity of the new number one determined by how the next few days in Melbourne pan out.

And while Clijsters, seeded 11, is some way adrift due to her injury-enforced absences, she showed enough today to prove she belongs among the elite.

She set the tone early on by breaking in the first game and, although Wozniacki hit back, further breaks in the third and seventh games handed her the opener on her fifth set point.

And when she broke twice more for a 5-2 lead it looked all over.

But Wozniacki fought back as Clijsters’ hitherto flawless game started to crumble amid a flurry of unforced errors.

Having taken it to a breaker, however, Wozniacki ran out of steam and Clijsters regrouped to come through.

Earlier, Azarenka moved into her second grand slam semi-final after hitting back from a shocking tie-break to beat Agnieszka Radwanska.

The third seed from Belarus struggled to make any inroads against the more consistent Radwanska early on but upped her game impressively to progress 6-7 (0/7), 6-0, 6-2.

The first set saw numerous breaks of serve with neither player capable of stringing more than two games together.

Pole Radwanska looked the more comfortable with the occasionally volatile Azarenka becoming frustrated with her game and the actions of the crowd, who were again mocking her grunting.

Azarenka held it together to break for a 6-5 lead only to be broken herself as Radwanska took it to a tie-break she dominated as her opponent’s powerful baseline game fell apart.

In previous years, that would often signal the beginning of the end for Azarenka but her new-found maturity again came to the fore as she bounced back in determined fashion, reeling off seven games on the spin to level it up and edge ahead in the decider.

Radwanska broke the slump to level it at 1-1 but Azarenka nudged 3-1 up and then broke again for 5-2. She held her nerve impressively when serving it out to advance to the last four for the first time in Melbourne.

“We just cannot play two sets, we have to push each other to the limit,” she said.

“We played some great tennis and I am really glad I could stay tough and see it out at the end.

“I am a year older and wiser, so I take it step by step, play every point and give the best I can and the result will be the result.”

As for the crowd, Azarenka was in forgiving mood, adding: “The crowd don’t distract me at all, thank you for being here, it means a lot.”