TENNIS/US Open:Justin Henin, the world number one and reigning French Open champion, has dropped only 11 games on her way to the quarter-finals of this year's US Open, a title she won in 2003 in an all-Belgian final against Kim Clijsters, now retired.

She had the need to conserve her energy, for now she may need to beat the Williams sisters back to back if she is step out into the Arthur Ashe Stadium on Saturday evening for the 11th grand slam final of her career.

First up is Serena, whom Henin has had to play at this same stage twice already this year, beating her at both the French Open and Wimbledon. This, in itself, is an onerous enough task.

To face Venus in the semi-finals would, in the minds of many critics, be a match too far for the comparatively slight Belgian, who like Venus has won six slams, two fewer than Serena.

Richard Williams, the enigmatic father of Venus and Serena, believes Venus, this year's Wimbledon champion, to be the favourite for the title here: "She looks like she is really enjoying herself out there more than Serena right now."

Serena has not played since Wimbledon, where she injured a thumb when she fell, suffering from cramp, while playing Henin.

"We know each other pretty well. Everybody has been waiting for this match since the draw, and here we are. It's great for me," said Henin, after crushing Russia's Dinara Safina 6-0, 6-2 in the fourth round under the floodlights.

"New York is a bit crazy and US Open is just a different kind of atmosphere from the other slams, but it has good memories for me."

There was a time when Henin hated playing under the lights.

"That was something I was really scared about because of my contact lenses," she revealed.

"Then after I became number one for the first time four years ago I had to play a lot in the night sessions. It's pretty electric in the night."

Henin recognises that Serena will have the edge playing in New York, although it was a massive psychological boost to beat her on grass at Wimbledon, even though it so drained the Belgian of energy that she lost so surprisingly to France's Marion Bartoli in the semi-finals.

Hence the argument that the possibility of having to beat two Williamses here will be one sister too many, and Henin has never played them back to back in a slam.

Venus plays Jelena Jankovic in today's other quarter-final, the Serb having made her slam breakthrough here last year when she reached the semi-finals before losing to Henin.

Her Serb compatriot Ana Ivanovic was totally subdued by Williams in the fourth round, and Jankovic may struggle to do any better.

With Maria Sharapova, the number two seed and reigning champion, losing in the third round, the opposite half of the draw is wide open, with Russia's Svetlana Kuznetsova, the 2004 champion and number-four seed, stiffening her challenge with a 6-2, 6-3 fourth-round victory over Victoria Azarenka of Belarus yesterday.

Meanwhile, the American Andy Roddick, seeded five, reached the last eight of the men's singles yesterday when the number-nine seed, Tomas Berdych, retired because of illness.

Roddick - who won this event four years ago and was the runner-up to Federer here last year - held a 7-6 (8-6), 2-0 lead when Berdych quit with a stomach ailment.