Sharapova shows signs of best as Russian army marches on

Tournament favourite joins Safina and Kuznetsova in the fourth round

There was another wobble, albeit a stately one, before Maria Sharapova took her place among the last 16 of those chasing Justine Henin's women's crown at the French Open. Sharapova, the top-seeded favourite to collect the only Grand Slam missing from her collection, will need to sharpen up her act for the tournament's second week, starting with her fourth-round match against fellow Russian Dinara Safina.

In yesterday's third round the opposition on offer to the reigning Australian Open champion seemed very ordinary, a 20-year-old called Karin Knapp (pronounced Kernapp) from the German-speaking South Tirol area of northern Italy. Having got to the third round of Roland Garros in 2007, her debut year, Knapp was runner-up in Antwerp this year to Henin, her best achievement on the tour to date.

How this sturdy girl decked out in shocking pink had done so well in Antwerp was rapidly obvious: she gives the ball a hearty wallop and has durable wheels. For almost all of this two-hour occasion this served her well against a Sharapova in one of her more vapid moods. The Russian had dropped sets in both earlier rounds and, so wayward were her serve and forehand once again, it seemed that she might drop another, or even disappear altogether.

Sharapova was well aware of this state of affairs, berating herself on a regular basis as she laboured to get her game on track. In the opening set, which dragged on for 81 minutes, she simply could not pull herself free of the dogged Knapp. Even a break of serve which put her 4-3 ahead was wiped out as Sharapova served for the set at 5-4 only to drop it on a double-fault. So the tie-break, and a rare surge of confidence from Sharapova with four successive points, put her in command of that and, with relief, the opening set.

Still Knapp stuck in there, with Sharapova aiding her opponent by unerringly opting for the wrong shot time and again. After another multi-deuce game lasting more than a quarter of an hour, the Russian suddenly shook herself clear, as if reminding all of us that this was not the authentic Shazza. She captured that game, and the Italian serve, with three great shots in a row – drop, backhand cross court and thumping forehand – and at last was off and running. For Knapp it was all rapidly downhill, a familiar feeling perhaps to someone who is an expert skier.

Knapp salvaged a mere four points from the last four games to go down7-6 6-0, and two of those were Sharapova double-faults, which have now totalled 37 in three rounds. "Today was an improvement," she claimed, "but it's fine, I have double-faulted an immense amount of times in my career. With my shoulder [injury] last year I was worried about hurting something more. That was always on my mind. But things will be fine."

Sharapova admitted: "The first week has not been good. But the second set today was a lot better and you just hope to improve with every match. No matter how you prepare it is always difficult going into a Grand Slam. I have been lucky to get through these matches not playing my best tennis and today was another step up."

As for Safina, a winner in Berlin this month, Sharapova sums her up as someone "who is playing with a lot of confidence on a surface she likes." Safina put away the Chinese Jie Zheng with increasing difficulty, 6-2 7-5, before stating her intention of being aggressive against her compatriot: "It's the only way." Safina also emulated her older brother, Marat Safin, with dismissive comments about tennis on grass, calling the season "in the middle of nowhere, only in England and Holland are there grass courts. I don't like grass courts, so they can take it away."

A new women's champion is guaranteed this year following the shambolic exit of Serena Williams, the last of the previous winners, on Friday. Henin's preferred choice of successor is Svetlana Kuznetsova, and it is beginning to look a wise one after she demolished another Russian, Nadia Petrova, 6-2 6-1 on the main show court at a time of weekend morning when Parisians are rarely astir. The few who gathered were treated to an impressive display of power by the rugged 22-year-old who won the US Open four years ago and was runner-up here in 2006.

Turned out all in black, relieved by a white sponsors' headband, Kuznetsova is built along the lines of a Navratilova and there were times when she operated at this distinguished level as she dismantled Petrova in 69 minutes.

The new level of power is down, she revealed, to a remodelled service action which is just settling down. "I feel so much power in it, so much more consistent," said Kuznetsova, who attributed her hard work ethic to the fact that she comes from a family of high calibre cyclists. As for her chances of winning in Paris, and helping to make her pal Henin happy, she said, "Why not? There are a few who have a real shot at winning it and I hope one of them is me." Kuznetsova will next face Victoria Azarenka of Belarus, who had never previously been beyond the first round here. Azarenka had the easiest of 6-1 6-1 victories over an Italian, Francesca Schiavone, who was playing with an adductor strain sustained in practice.

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