Williams turns on power to destroy poise of Petrova

Perhaps it was the unseasonal rain that unsettled players at the Australian Open here yesterday. The retractable roofs over the two main courts remained closed for most of the fifth day as the mood frequently matched the grey skies over Melbourne Park.

Nadia Petrova, the No 5 seed, lost her self-assurance - and the match - against Serena Williams. Gaël Monfils, the crowd-pleaser from two nights earlier, could not concentrate on the task in hand ("I wasn't there on the court," he explained enigmatically) and was beaten by his friend and fellow Frenchman, Richard Gasquet. A tearful Wayne Arthurs, the veteran Australian, bowed out on his final appearance here after only three games when an anaesthetic injection left him with no feeling in one leg. Marat Safin, whose behaviour was at least in character, lost his rag with the umpire on his way to defeat against Andy Roddick.

While the roofs keep spectators and television executives happy on rainy days, they inevitably change the nature of the tournament. When Petrova and Williams began proceedings under floodlights in air-conditioned comfort at 11am, it could have been a match at any indoor tournament in any stadium in the world.

More trying conditions might have favoured Petrova, clearly the fitter of the two, though the match was lost in the head rather than the legs. Petrova is a fine player, as she demonstrated with five titles last year, but has yet to prove she can cut it on the biggest stages against the biggest names.

The Russian ran away with the first set and led 5-3 in the second. Williams, however, kept going for her shots and her opponent's game fell apart. The 2003 and 2005 champion won 1-6, 7-5, 6-3. Petrova probably regretted her pre-match comments that Serena and Venus were not the force they were and that "everything is leading towards the end of their careers".

After the match, Petrova admitted that she had made too many mistakes. "Serena raised her game a bit and I started to be a little bit more careful," she said. "She started putting more pressure on me and she broke my serve. I didn't serve great. I still fought my way back and was serving for the match, but she came up with some unbelievable returns."

It was Williams' first victory over a top-10 player for two years. Injuries and a sheer lack of matches (having played just five tournaments in 16 months before returning in Hobart last week, she has slipped to No81 in the world rankings) have left her well short of peak fitness, although she insisted at the end of this match that she would have happily carried on playing.

While Williams can hit with formidable power and remains a ferocious competitor, a result like this must cast doubt over the strength in depth of women's tennis. It is hard to imagine a male player in a similar physical condition being able to beat the world No 6.

Williams' next opponent is Jelena Jankovic, who in the opinion of many - including Andy Murray's coach, Brad Gilbert - is a dark horse for the title. The 21-year-old Serb, who blew a winning position in her US Open semi-final against Justine Henin-Hardenne last year, has beaten Williams in their last two meetings.

If she does beat Jankovic, Williams' next scheduled opponents are Svetlana Kuznetsova and Amélie Mauresmo, who enjoyed straightforward victories yesterday over Maria Kirilenko and Eva Birnerova respectively.

The heavyweight men's encounter of the day saw Roddick beat Safin 7-6, 2-6, 6-4, 7-6. The American was watched by Jimmy Connors, whose journey Down Under had been delayed by the death of his mother. Roddick's confident backhand and crisp volleys were evidence of his coach's influence since they joined forces last summer.

Safin exploded when Wayne McKewen, the tournament referee, ordered play to resume after the court had been dried - and the roof closed - following a shower. The Russian thought it was still too wet and protested at length, initially refusing to play. Thereafter he had several heated exchanges with umpire Pascal Maria and was officially warned for swearing.

Roddick now plays Mario Ancic, but the match of the fourth round should be Roger Federer against Novak Djokovic. The world No 1 beat Mikhail Youzhny in straight sets, while the 19-year-old Djokovic beat Danai Udomchoke in four.

Two more of the new generation met in the Vodafone Arena. Monfils, a bundle of nervous energy, had won the crowd's hearts with his thrilling victory over Marcos Baghdatis but looked ill at ease against Gasquet, who lost only six points in the first set on his way to a 6-0, 4-6, 7-5, 6-3 victory. "In the first set I wasn't there on the court," Monfils said. "I wasn't very focused."

There was nothing wrong with the focus of 35-year-old Arthurs but everything wrong with his right leg after an anaesthetic injection for a hip injury. "I had no co-ordination, no feelings in my right leg at all," Arthurs said following his retirement against Mardy Fish after only three games.

The Melbourne resident had been hoping to reach the fourth round for the first time in his career in his 16th and last appearance at his home tournament. No wonder the tears flowed. "I couldn't really believe that this was the way that my last Aussie Open was going to finish," he said.