Is there still major life in Venus?

Martina Navratilova sent a text message to her friend and doubles partner, Lisa Raymond, yesterday morning, telling her: "Just be brave and believe in yourself." Raymond heeded the advice and, a few hours later, defeated Venus Williams in straight sets in the biggest upset of the Australian Open.

The protection of a No 3 seeding could not save Williams, making a comeback after six months off the circuit, from her worst Grand Slam result for nearly three years. "I'm pretty much in shock," she said after her 6-4, 7-6 loss. "I definitely had some high hopes to do well here and ultimately to win."

Her nemesis came in the unlikely shape of Raymond, a doubles specialist who has only won three singles titles in her 14-year career and had never before taken even a set off Williams. But the 30-year-old American played some of the finest tennis of her career to oust last year's runner-up, keeping her under pressure throughout the 89-minute encounter.

A glowing Raymond said it had been the match of her life. "I knew I had to come in, step up to the plate and just go for it," she said. "It was the only way I was going to win. I couldn't ask any more of myself today. I played an incredible match."

The No 25 seed, whose best Grand Slam singles performance was reaching the quarter-finals at Wimbledon in 2000, added that Williams and her sister, Serena, had "certainly lost a little bit of their lustre".

Venus suffered an abdominal injury after being beaten by Serena in last year's Wimbledon final, and did not play competitively again until she arrived in Melbourne. A four-times Grand Slam winner, she has not captured a major title since 2001. Her sister, still recovering from knee surgery last August, did not come to Australia to defend her crown.

Venus got off to a slow start in yesterday's third-round match, losing her first two service games and giving Raymond the first set on her fifth set point. Raymond kept up the aggressive tempo in the second set, breaking serve in the first game, but Williams produced serves of up to 125mph and the pair traded breaks to reach 3-3. Williams saved one match point in the tie-break with a backhand cross-court winner, but sent a forehand return wide to seal her fate.

The world No 11 fired 14 aces and made 44 unforced errors, repeatedly playing to Raymond's lethal forehand. She said: "She hung in there and played a lot of good shots and was really determined. In the tie-break, I probably went for too much, too soon."

Williams said: "It's definitely going to settle in this evening. It will be like 'No!' That's the way it is. You win some, you lose some. The best player wins. Unfortunately it wasn't me in this fortnight."

With the exception of the 2001 French Open, when she lost in the first round, this was her worst Grand Slam result since her debut season in 1997.

Her exit bolsters the chances of the few remaining top seeds, including Kim Clijsters, the No 2, who cruised into the fourth round following a 6-2, 6-1 win over Russia's Dinara Safina, the younger sister of Marat Safin. Clijsters said, however, that she was taking nothing for granted, observing: "Anything can happen."

The Belgian said she was surprised by Williams' loss, but expected her to rediscover her form soon. "I think she just needs a few more matches and she'll be back on track."

Clijsters, a semi-finalist in 2003 and 2002, next plays Italy's Silvia Farina Elia, the 20th seed, who recovered from one set down to beat Amy Frazier 4-6, 6-1, 7-5.

Raymond will meet Tatiana Golovin, the French teenager who claimed her second seeded scalp when she overcame Russia's Lina Krasnor-outskaya, the No 23, in straight sets. Golovin, who turns 16 today and is playing in only her second Grand Slam, has surpassed her own expectations. "My goal [in Melbourne] was to pass a few matches, get a few points," she said. "I just started to play really well."