Key Biscayne, Florida.

Shaughnessy, a 23-year-old from Arizona, ranked No 22 in the world, had defeated Williams only once in their previous six matches, in Stanford in 2001. Instead of wailing about the Williams sisters being too strong for everybody else, Shaughnessy decided to join the Athlete's Performance training programme and has gained 15 pounds of muscle over the last two years.

"Women' s tennis has become more and more physical," she said, "and I felt I needed to take my physique to another level. My whole body has changed, I'm much stronger, faster, more flexible and more durable. When I walk on the court, there's not anybody that's going to beat me because I got tired or I wasn't fast enough. It's a confidence booster knowing that."

Shaughnessy, who uses hypnosis CDs to give her "positive thoughts", was too good for her fellow countrywoman, who won the hardcourt title here in 1998, 1999 and 2001. "I listen to the CDs at night to put what I want to have in my mind," Shaughnessy told reporters. "It's just something I do for myself to have positive thoughts in my mind and be at peace with myself."

The hours spent crunching and cranking served Shaughnessy well when she had to respond to Venus's powerful early burst. After Williams raced into a 3-0 lead, the 23rd seed began to dictate the pace of the match. She clawed her way back to to 3-3 - losing only one of 12 points in the process - and raced through the tie-break, 7-2. At that, Venus folded, losing her second service game of the second set to love, failing to land a first serve in the process. Meghann swept to a 5-0 lead in the second set with some deadly service returns and it was only nerves on the part of the 23-year-old that prevented her completing a second-set whitewash. Only in the concluding two games, which took more than 20 minutes, did Shaughnessy's nerve waver. Williams saved eight match points - but Shaughnessy, 23, was too strong on this night to be denied. She attacked Williams' forehand with a vengeance. She hit short forehand crossing shots for winners. She hit an involuntary backhand volley for a deep winner, and even uncorked a 106-mph second serve on her ninth match point.

This was the second time that Shaughnessy had beaten Venus in their seven meetings and represented the first time that the elder Williams had lost to anyone but Serena in a completed match since last September, when Magdalena Maleeva, of Bulgaria, prevailed in Moscow.

It's impossible to win every match," Williams said. "I could not seem to get the ball to go in today. It's disappointing to lose, but she hit a lot of good shots."

Shaughnessy, on the other hand, could not contain her satisfaction at the manner of a victory that sets up a quarter- final today against Jennifer Capriati, from whom she has taken only one set in six matches.

Match Summary

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