Williams machine powered by dual fuel mixture

Nine of the last 11 Wimbledon championships have been won by one or other of the American sisters, a record which is one reason why, despite both having been largely inactive over the past year, they again feature among the favourites this time around. They have nothing to prove.

The same cannot be said of their rivals. While victory for Serena or Venus would be among the most remarkable of their careers given their injury problems, they would also cast a larger shadow than any of their titles over opponents such as Maria Sharapova and Caroline Wozniacki.

The past year or two have seen more contenders for the majors than for some time, with Li Na and Francesca Schiavone winning titles, Samantha Stosur getting to the final in France and Wozniacki reaching the No 1 spot in the rankings.

The greater competition has led to suggestions that there has been a levelling up in the women's game. A successful Williams comeback over the next fortnight, however, would provide pretty compelling evidence that it has, in fact, been a levelling down.

Defending champion Serena, who beat 2004 champion Sharapova and Li before defeating Vera Zvonareva in a one-sided final, has hardly played since. First she needed surgery and the rest of the year off after cutting her foot stepping on broken glass, and then this March she became seriously ill with a lung condition.

She made her return to action only weeks ago, at the Aegon International in Eastbourne, and although she won her first match against Tsvetana Pironkova, she lost her second against Zvonareva, a long three-setter.

Venus's troubles have been less severe. They began when a hip injury forced her to pull out of the Australian Open, and the condition forced her to miss the French Open, which thus became the first Grand Slam for eight years in which neither sister had competed. She made it through two rounds at Eastbourne before losing for the first time in 11 matches to Daniela Hantuchova.

Venus is seeded 23rd at these championships, Serena seventh. Those seedings are recognition of their past achievements, not of their current standing in the rankings, but if either is able to play her way into match fitness by coasting through a couple of early rounds, the seeding committee will feel their calculations have been justified.

At times in the past, both sisters have voluntarily taken breaks from the tour in order to pursue other interests or recharge their batteries, but yesterday Serena explained that, although her absence this time had been so long, she never felt tempted to call it a day. "No, never," she said. "I always thought I would want to continue to play. You know, I thought I would play a lot sooner; things didn't work out.

"But you know, I'm never the type to stop. You know, I'll stop when I'm ready, and I'm just not ready. I really thoroughly enjoy being out here."

The relish with which she said it may well have provoked some fear in her rivals, for when Serena is enjoying her tennis, you can bet there is someone on the other side of the net who is having a very hard time of it. The first woman who is likely to have that experience this year is Aravane Rezai of France, whom the defending champion will meet on Centre Court tomorrow. Possible opponents after that include former finalist Marion Bartoli and ex-world No 1 Ana Ivanovic, and then a quarter-final could loom against Li. If she gets past that, Serena is likely to face a semi against either Sharapova or top seed Wozniacki.

Venus is on the other side of the draw, which keeps alive the possibility of another family final. She opens up today against Akgul Amanmuradova of Uzbekistan, then could face Jelena Jankovic, another former world No 1, or Zvonareva, this year's No 2 seed. Her possible quarter-final opponents include eighth-seeded Petra Kvitova and No 12 Svetlana Kuznetsova, with a semi against Schiavone or No 4 seed Victoria Azarenka lying in wait after that.

Although she is here and apparently ready to play, there is a doubt - as there has been for two or three years now - over Venus's application. Tennis, and proving she is extremely good at it, is not a motivating factor the way it once was.

For Serena, on the other hand, the hunger is very much still there. She may only have played a couple of matches since returning to competition, but she has spent many long sessions in the gym - and her hard work has already paid some dividends, as was shown when she was able to go toe-to-toe against Zvonareva for almost three hours. Asked yesterday if she had felt exhaustion after that three-set battle, or any kind of adverse reaction in her breathing, she replied confidently in the negative. "No, I didn't," she said. "That was a blessing - I didn't feel anything after a three hours' match.

"I felt like the breaks were five seconds long. Every time I sat down, the umpire would call time. But I felt like I was able to go through it.

"I was fine physically when I got off the court. I didn't feel anything. I felt fine and I ran a lot and I felt good. I still feel pretty good.

"I talked to my doctor almost every day before I left, and he said I'll be fine. I said, 'So can I pretend this never happened?' He said, 'Yeah, just pretend this never happened and you'll be fine.'

"I just had to get my lungs into better shape. I'm probably actually in better shape running-wise than I was before. I have to do things differently 'cause I had to expand my lung capacity, because I lost a little bit of my lung. So I had to expand it and just work on it and do better."That hardworking, indomitable attitude will surely be enough to make Serena a contender again this Wimbledon. Whether her awe-inspiring mental toughness is enough for her to overcome her lack of physical conditioning and actually retain the title is another matter - one to which Sharapova, in particular, could supply a negative answer.