It almost came as a shock to see Maria Sharapova have to fight to win a match on grass. It was even more surprising to hear her admit it.

The Wimbledon champion dropped a set for only the second time in two years at the DFS Classic before defeating Samantha Stosur of Australia 6-3, 3-6, 6-1 in an intriguing match here on centre court yesterday.

Sharapova, the 18-year-old Russian, will play Eleni Daniilidou of Greece in the quarter-finals today. If Daniilidou comes close to fulfilling her own potential (which, these days, is open to debate), Sharapova will face another fight.

It is easy to know when Sharapova is facing pressure. The left fist becomes perpetually clenched, the eyes become narrow, and the demeanour becomes rigid. If she was not so good at tennis, she could easily become a prodigious actress.

?I knew it would be difficult because I have played her [Stosur] before,? Sharapova said. ?She served and volleyed a lot more and made a lot more first serves than she did before. She did not make a lot of errors at the net so she was always putting pressure on my return.

?I had to fight for it. She pushed me hard. But it is good to have matches like these because they are the kind of challenges that I relish. It is what champions are all about.

?You might not be playing your best tennis, or maybe your opponent is playing great tennis, and it comes down to the wire. You have to figure out a way to win and you do win.

?That comes with experience, obviously, but it is important to learn from your match and take those lessons into the next match.?

The problem for Stosur was the awe that exists around Sharapova. It is almost like a protective coat. Even when the Australian was dominating, and providing fine examples of grasscourt tennis, Sharapova seemed unlikely to lose.

Even when it was easy to lose concentration ? the match was held up for five minutes for a waitress to receive treatment court-side before being taken to hospital after falling through a gap in the hospitality stand ? Sharapova retained her composure.

It might have been different had Stosur been more confident. She has the serve and the range of shots to trouble any player on grass, but seeing out points posed something of a problem. On another day, she might have won.

?I knew I had to be aggressive and dictate to her and, for the most part, I was able to do that,? Stosur said. ?It was definitely the right way to play.

The match was won and lost in the fourth game of the final set. Stosur made a hash of a volley at the net and crumbled.

It did not seem to matter that Sharapova?s serve was letting her down. That, at least, was the verdict of her father, Yuri Sharapov , who could not conceal himself if he tried. He was strident throughout and was seen afterwards talking to his daughter about her serve.

?I think I am serving well,? Sharapova said. ?I was only broken once.?

Daniilidou, a semi-finalist two years ago when she was in the world?s top 20, booked her place in the quarterfinals with a 6-3, 6-3 victory over eighth seed Ai Sugiyama of Japan.

Sharapova should win today. Daniilidou has a beautiful grass-court game and her backhand is a joy to behold. But her decline from No 14 in the world to No 88 in two years has been emphatic. In the same period. Sharapova has gone in the other direction and is now world No 2.

Retaining the DFS Classic crown will not improve that ranking but it will improve her chances of retaining her Wimbledon title.