“I didn't say I'll kill you, are you serious?” Serena Williams was aghast that anyone might suggest she would countenance such a thing let alone say it on an open court.

John McEnroe - his copyright on the “S” word exploited - responded with incredulity while he suffered a serious case of the flashbacks in the commentry box. Nineteen years ago, at the Australian Open, McEnroe was given his marching orders and confessed that he had forgotten where he was, what he was saying and what effect his words would have.

That blistering summer's day in Melbourne, McEnroe's verbal abuse of Ken Farrar, the ATP supervisor, was heard by three people; Farrar, Peter Bellenger, the referee, and Gerry Armstrong, the British umpire who was told to call “Code violation, verbal abuse, default Mr McEnroe, game, set and match, Pernfors” (Mikael Pernfors, the Swede). On a cool Saturday evening here, Williams lost control as the world eavesdropped.

“If I could, I would take this ball and shove it down your throat and kill you (several “F” words have been removed)”, she told the lineswoman who had called a foot fault on a second serve at 15-30, as she trailed Kim Clijsters, the Belgian, 6-4, 6-5 in the US Open semi-final. There was no alternative but to send Williams packing. Within a few minutes, the offending tape was posted on YouTube, the public had had its say and the defending champion was a universally condemned woman. They will have been swooning at Wimbledon yesterday morning because this was not the kind of behaviour expected of a member, especially its ladies champion.

Tennis has its rules and Williams abused this particular one. The foot fault (no part of either foot should touch the line before the ball is struck) is a call that aggravates and unnerves those players caught offending - I have seen many that went unspotted and more that were called that almost certainly were not - and for an official to be certain of a transgression at a delicate stage of a grand-slam tournament and call it requires a high degree of concentration and bravery (some might say foolhardiness).

When she heard the call, the heart of Louise Engzell, the umpire, must have sunk. She knew that Williams would have something to say on the matter, although for a few seconds it looked as if the American would accept her fate and serve again. Then, something clicked inside her head, there was much scary waving of racket under the lineswoman's nose - à la McEnroe in Melbourne - and choice, scathing words were uttered.

Once again, there was a hiatus while the lineswoman collected her thoughts. Had Williams really said what she thought she had said? There are effects microphones all over Flushing Meadows to pander to this increasingly voyeuristic world.

Engzell listened to the lineswoman's version of events and called for reinforcements; the lineswoman went back to her chair, Williams approached her again the line judge returned to the security of the umpire's station where Brian Earley, the referee and Donna Kelso, the Sony Ericsson WTA Tour supervisor, digested the implications and prepared to tell Williams that her violation for unsportsmanlike conduct meant the end of her championship.

Clijsters, taking it all in at the opposite end of the court, had her mind fixed firmly on thumping the next Williams serve back and passing the sixth stage of the most improbable seven in tennis history. The next thing she knew, Williams was walking towards her, hand outstretched.

What was all the more remarkable was the calm manner with which the New York crowd accepted the American's fate. Past audiences here would have ripped the place apart.

How apt that, during the day's delays, they should have replayed the incident 30 years ago when a second-round match between McEnroe - him again - and Ilie Nastase was interrupted when Frank Hammond, the umpire, called a penalty against the Romanian for delay of the game and the furore created was such that Hammond was replaced in the chair by Mike Blanchard, the referee, before the match could resume.

They do not have loose seat cushions here any more, for which Williams must be grateful. In winning 11 grand-slam singles titles, she has performed in a manner that has transfixed the world and raised the performance bar such that the women's game is vastly more energetic and physically aggressive than ever. She and Venus, her sister, neither courted popularity, nor always found it. They are driven athletes who have done things a certain way and if those watching did not like it, they could look the other way.

They profited while the rest of the world played catch-up and suddenly, these past few weeks, have been astonished that Clijsters, having taken more than two years away from the game to start a family, has returned, reinvigorated, at a level of physical readiness that has staggered everyone, and has now beaten them both on the way to last night's final. She would have preferred to win the match on a winner, rather than the tumultous manner of Williams's verbal onslaught, for which she has been fined $10,000 (about £6,000) - plus $500 for racket abuse - and, given the severity of the profanities, may yet face a suspension.

The Williams family, as ever, drew the coaches around themselves yesterday. Richard Williams, Serena's father and coach, was talking to Kevin Garnett, the NBA star, when reporters approached him for a comment. “Just get out of my face,” he said. Oracene, her mother, while accepting that the end of the match was “startling”, defended her youngest daughter, saying, “I think she should speak up for what is right.” Unfortunately, in this instance, she spoke up a little too loudly.