Women, we are regularly told, are unpredictable and the only thing that is definite in this most uncertain of French Opens for the women players is the fact that there will be a new champion.

Should Maria Sharapova somehow prevail and complete her set of Grand Slam titles, it will not only be a triumph over a phobia of her least favourite surface, but victory over the nagging self-doubts that haunt even the most seemingly self-assured of performers.

On the surface, Sharapova is the 21-year-old who has it all: enormous wealth, photogenic beauty, sufficient endorsement contracts to fill the portfolios of several agents and, most recently, the world No 1 ranking after the retirement of Roland Garros’s reigning champion Justine Henin.

If the top seed can take a positive frame of mind, she is on course to become the first woman since Steffi Graf 20 years ago to win the revered Grand Slam in the same calendar year. On top of Henin’s absence, Sharapova’s chances of success were improved considerably by the elimination of the Williams sisters in the space of a few hours on Friday. Admittedly both Serbs, Ana Ivanovic and Jelena Jankovic, remain distinct threats, but Sharapova has three major titles compared to their total of zero.

However, the American-based Russian’s confidence at achieving her aim has edged marginally above minimal. A forceful conclusion to her third-round win over 38th-ranked Karin Knapp only partially brightened her mood after two matches and a set of such gross ineptitude that she wondered whether it was somebody else out there on court clad in her midnight blue outfit.

Certainly Sharapova did not have the aura of a champion in waiting as she relaxed after her 7-6 6-0 win over the 20-year-old Italian. “For the last couple of days I’ve felt it was like a different person out there,” she said. “It was as if my twin sister was here and then Maria actually made her flight and got on court for the second set. I’d just been really hesitant the last two rounds, not really being aggressive. Not playing my game.”

The same could most certainly not be said of the two Serbs who are Sharapova’s main rivals. Neither has dropped a set and Jankovic showed no ill effects from the arm injury that troubled her in her previous round to beat 28th-seeded Slovak Dominika Cibulk-ova 7-5 6-3. Meanwhile, Svet-lana Kuznetsova, the fourth seed who remains the only other player left in the tournament to have won a major title – the 2004 US Open - followed up two comprehensive wins with a brutal destruction of what remains of the brittle self-belief of Nadia Petrova, winning 6-2 6-1.

If Sharapova progresses, the chances are Kuznetsova will be waiting in Thursday’s semi-final, but two tasks are paramount for the world No 1 before she can even contemplate the encounter.

The first is to recapture the serving form that was so integral to her winning Wimbledon nearly four years ago, the US Open in 2006 and the Australian Open at the beginning of this year. The second is to purge an horrendous memory of an appalling choke against fellow Russian Dinara Safina at the same stage of the French Open two years ago.

Thus far in this tournament she has been plagued with double faults - nine more against Knapp took her running total to 36, which is bordering on calamitous. At the same stage at Melbourne in January she had hit eight. Clearly the shoulder problems which plagued Sharapova for much of 2007 are still a factor.

Sharapova had been able to use blustery conditions as an excuse for the 17 double faults in her opening match against debutante Evgeniya Rodina, but the flags above Court Philippe Chatrier were barely moving throughout a first set that lasted one hour 21 minutes with Knapp.

Her opening serve of the match was a sign of things to come, thudding into the net less than a foot above the clay. Her indecision became even more apparent as she aborted her second serve in the middle of tossing the ball and sauntered back behind the baseline to regroup.

Regularly, at times of pressure, Sharapova double-faulted. Normally just a rise in the deci-bels of her grunt is sufficient to ward off anxiety, but these are testing times for her conviction.

Sensing her esteemed opponent’s troubled state of mind, Knapp tried to rile her into further errors by standing a yard inside the court to return.

“When your opponent has so many looks on second serves it’s challenging,” said Sharapova. “I don’t care if it’s clay or hard or grass, you don’t want your opponent to have a hit on it or see them stepping into the court.”

Knapp’s resistance was only temporary and after Sharapova wrenched control of the tie-break with some forceful and noisy groundstrokes, she drove home her dominance in the second set. It took a self-berating shout of “Oh my goodness, Maria!” to force her into action, but once in control the quality of the Russian’s tennis began to soar. After initially struggling to make inroads on Knapp’s strong serve, she took the ball earlier on the rise and secured victory in under two hours.

Sometimes when she blows victorious kisses to the four sides of the stadium, it seems no more than routine. This time Sharapova seemed to be genuinely relieved, but no sooner had she walked off court after her win, than any form of elation was tempered by the realisation that her next match would be against Safina, ranked 14th in the world and on the rise after winning her first-ever Tier One title in Berlin last month.

There are some matches that are never forgotten by even the most accomplished of performers and Sharapova still agonises over allowing a 5-1 lead in the final set against Safina in 2006 to erode into a 7-5 2-6 7-5 exit.

“That’s one match that I don’t want to remember,” she said, mindful of the fact that Safina’s first two victories of this tournament saw her drop just four games and there was little more resistance to her from China’s Jie Zheng, the Muscovite winning 6-2 7-5.

The top seed continued: “It’s going to be a new day, and I’m obviously going to have to perform better than I have. Right now she’s playing with a lot of confidence and is also on a surface that she likes and grew up on as well.”