If momentum counts for everything in tennis, nothing will stop Serena Williams  from winning the French Open  for just the second time in her career in Paris on June 8. At 31, the superstar of the women's game is on an unprecedented winning run going in to the consecration of the claycourt season at Roland Garros. Four straight tournament wins at Miami, Charleston, Madrid and Rome (the last three coming on clay) and 24 matches in all for the loss of just four sets represents the best unbeaten streak of her career. Nothing suggests that is about to end in Paris. And yet there are demons to be confronted for the American diva in the city she says is her favourite place in the world. Namely, 11 previous campaigns and just the one championship win — in 2002 when she defeated sister Venus in the final — as the first step on the road to her famous "Serena Slam" of all four Grand Slam titles. Since then a combination of injuries, lack of focus and claycourt calamities have brought losses to the likes of Katarina Srebotnik and, most surprisingly, in last year's first round to France's Virginie Razzano, which saw a frustrated Williams stomp off the Philippe Chatrier Centre Court in a decided huff. Since her 2002 triumph, amazingly she has only once managed to get past the quarter-final stage. But, on the face of it, all that is about to change. All but down and out after missing 11 months in 2010 and 2011 with a right foot injury followed by a life-threatening pulmonary embolism, Williams has re-dedicated herself to her sport and the results have been hugely impressive. Last year's debacleA repeat of last year's debacle, she says, is out of the question — the lesson has been learned. "I have been playing a lot more tennis.I have been spending more time on the court," she said at Roland Garros on Friday. "I felt this past year coming back I had nothing to lose and just really wanted to enjoy my career. You know, in the past when I played I was always so stressed out and always wanted to win, win, win. "And now I'm definitely having a lot more fun than what I used to have on the court and really enjoying every moment of me walking out there." With no Justine Henin and Kim Clijsters around, and with sister Venus a non-factor on the red dirt, the main threat to Williams would normally come from defending champion Maria Sharapova of Russia or the best of the new wave, Victoria Azarenka of Belarus. But against Sharapova, Williams is 13-2 head-to-head and against Azarenka she is 12-2. She has never lost to either on clay, although all three would say that the surface is their least preferred. So what could get in the way of a 16th Grand Slam title for Serena? John McEnroe says that his own experiences of failing to win in Paris when being hot favourite gives him an insight. On any given day, things can go wrong. "I mean it's been done before. I've done it myself, but you sort of have to beat yourself. The level she's at when she's playing well, I don't think anybody can beat her. Anybody, no matter how great they are though, everybody has bad days. "On clay, it's her worst surface. The odds would increase. The pressure is greater obviously at the French because she's only won it once. I would say at some stage in the event, it would be likely that she won't have one of her best days. Depending on her opponent that day, someone might have a shot at her." Sharapova and Azarenka apart, the main challengers to Williams's supremacy are likely to be 2011 champion Li Na of China, last year's beaten finalist Sara Errani of Italy and possibly Samantha Stosur, if the Australian can develop her top spin attack. And then there is always the unpredictable Parisian weather at this time of year and the unforgiving public at Roland Garros, both of which have been unkind to the American in the past.