Sharapova overthrown by Che Guevara fan Petkovic

Maria Sharapova, the world's highest-earning sportswoman, lost to Andrea Petkovic, who admires Che Guevara and wants to form her own political party. Francesca Schiavone beat Svetlana Kuznetsova 6-4, 1-6, 16-14 after four hours and 44 minutes, the longest women's match in Grand Slam history. Caroline Wozniacki mischievously told reporters that she had been attacked by a baby kangaroo. Yes, it was a good day here at the Australian Open for those who insist that women's tennis is not dull.

There is no bigger name in the women's game than Sharapova, but the 23-year-old Russian's 6-2, 6-3 defeat in the fourth round yesterday inevitably cast doubts over her future. Since winning her third and last major title here three years ago the world No 16 has reached just one Grand Slam quarter-final. She has never been the same since undergoing shoulder surgery late in 2008.

Nevertheless, Sharapova gave no indication that she was ready to throw in the towel and concentrate either on the other interests that have made her such a success off the court or her forthcoming marriage to the LA Lakers basketball player, Sasha Vujacic.

"I've won many matches and been No 1 in the world and also had an opportunity to say that I've had enough," she said. "I could do many other things in my life. I have enough money. I have a great family around me. But when I was away from the sport, all I wanted to do was to wake up in the morning and put on my Nikes and go out there and run and play. When it was taken away from me I realised how much I loved it."

Sharapova, who made 30 unforced errors, was outplayed by Petkovic, a 23-year-old German who came from a set down to beat Britain's Anne Keothavong in the second round. She is through to her first Grand Slam quarter-final, in which she will play China's Li Na.

Born in Bosnia, Petkovic moved to Germany when she was six months old. A political science student who reads Oscar Wilde in her spare time, she intends to form her own political party "to raise attention for the young people in my country". She lists the people she most admires as "Goethe (genius in writing) and Che Guevara (genius in fighting)". The world No 33 is a fine athlete and performs a victory jig – the Petkodance – after her wins.

While Petkovic was winning in Rod Laver Arena, Kuznetsova and Schiavone were making history in the Hisense Arena, the second show court. They would have had to play for another six hours and 21 minutes to equal the longest men's match, established at Wimbledon last summer by John Isner and Nicolas Mahut, but the 30-year-old Italian and the 25-year-old Russian still smashed the previous women's record in a Grand Slam in the Open era which was set here last year, when Barbora Zahlavova-Strycova beat Regina Kulikova 7-6, 6-7, 6-3 after four hours and 19 minutes.

The statistics showed how close yesterday's marathon was. Kuznetsova won more points (181 to Schiavone's 177) and hit more winners (69 to 58), but she also made more unforced errors (68 to 67). It was an undistinguished match until the final set, which took on a three-hour life of its own as Schiavone twice failed to serve out for victory and Kuznetsova wasted six match points.

Kuznetsova scorned the first three, two of them with unforced errors, when Schiavone served at 7-8 and three more two games later. At 11-10 Schiavone had treatment for an abdominal strain while Kuznetsova sought help for a foot problem. With the Italian serving at 15-14 it was Kuznetsova's turn to save two match points, the second with a superb return of serve to her opponent's feet, but on the third Schiavone finally hit a winner to secure the most remarkable victory of her career.

Schiavone, who came from a set down to beat Arantxa Parra Santonja in the first round and beat Rebecca Marino 9-7 in the deciding set in the second, was so tired afterwards that she was hardly able to appreciate her achievement. "It was really fantastic for me personally," she said wearily. "I hope one day to show this DVD to my son."

In her 11 previous appearances here Schiavone had never gone beyond the fourth round. Yesterday's win takes her into the quarter-finals, where she will meet Wozniacki, the world No 1. Schiavone herself will climb from No 7 to a career-high No 4 or better in next week's updated world rankings list as she continues to enjoy a remarkable Indian summer to her career.

Kuznetsova, who has lost weight and worked hard on her fitness after her worst season for seven years, said she felt "very empty". The world No 26 said there were times when she had found it hard to think straight. "At some stage I was thinking: 'What's the score? Who's serving? What's going on here anyway?' Sometimes I didn't have a clue. It was so hard to count. I was thinking: 'Who is up? Her? Me?'"

Only one women's match has featured more games – Chanda Rubin beat Arantxa Sanchez-Vicario 6-4, 2-6, 16-14 here 15 years ago - and only one has lasted longer. Vicki Nelson-Dunbar beat Jean Hepner 6-4, 7-6 after six hours and 31 minutes at the Ginny tournament in Richmond, Virginia in 1984 – the tie-break alone took one hour and 47 minutes, with one point lasting 29 minutes and featuring 643 strokes. A local reporter kept count of the number of shots after a number of exceptionally long rallies.

Roger Federer equalled Jimmy Connors' record of 27 consecutive Grand Slam quarter-final appearances but posted a patchy performance in beating Spain's Tommy Robredo 6-3, 4-6, 6-3, 6-2. He now faces his friend and Davis Cup colleague, Stanislas Wawrinka, in the first all-Swiss Grand Slam quarter-final in the Open era. Wawrinka beat Andy Roddick 6-3, 6-4, 6-4 and is unbeaten this year, having won his first hard-court title in Chennai en route to Australia. Novak Djokovic beat Spain's Nicolas Almagro 6-3, 6-4, 6-0 and now faces Tomas Berdych.