SONIA O'SULLIVAN leaves Atlanta this morning to confront the deepest crisis of her career, in the privacy of her London home, after crashing out of the heats of the 1,500 metres in the Olympic Stadium yesterday.

For the second time in three days she sought to convert one of the most successful records in Grand Prix racing into the more enduring accolade of Olympic gold.

And, for the second time, it ended in tears and disbelief after she trailed in 10th of the 11 starters in a leisurely run race which was won by the Russian, Lyudmila Borisova.

Mercifully, this latest disaster occupied her, and us, for just four minutes 19.77 seconds, a staggering 21 seconds outside her personal best and six seconds slower than Borisova's winning time.

Within a matter of hours O'Sullivan presented herself for a medical test conducted by the Irish medical officer, Dr Joe Commiskey, and his assistant, Dr Conor O'Brien in a belated attempt to discover if illness was responsible for her startling decline in form.

In the sense that the 5,000 metres final had prepared us for the worst, it wasn't quite as shattering as last Sunday. And yet defeat, when it came, was equally incomprehensible.

She lined up for the start in the official Asics uniform of the Irish team with all the verve of an athlete who was primed to run well. There was little of the pre-race strain which showed on her face before Sunday's race and, given the low key atmosphere in the stadium at 10 a.m., that was to be expected.

Yet, before the race had reached the halfway point, there were signs that she was in trouble. As in the 5,000 metres final, she appeared to be wracked by self doubt, never able, it seemed, to determine where she should position herself.

At times she was with the pace, then she would fall back into the pack only to re emerge as a challenger for the lead. That was unlike O'Sullivan who is one of the most astute race readers around.

Even then we knew that she was in trouble but the pace (69 seconds for the second lap and 67 for the third) Was sluggish enough to enable her to extricate herself from the nightmare closing in on her.

Sadly, she couldn't and, while her legs were still moving, the stride became shorter and shorter to the point where it appeared to be covering little, or no, ground. Now she was in second last place with only the Bulgarian Patya Strashilova behind her as the leading group charged for home.

Once over the line she looked as composed as any of her rivals. There was no sign of physical distress, nothing to suggest that the stomach problems, which were advanced as the reason for her eclipse in the 5,000 metres, had struck again.

Back in the mixed zone area, where athletes, handlers and press converge, little had changed from Sunday. There were fewer tears now but that, almost certainly, was because bitter experience had prepared her for the worst.

Again, her father, John, was there to embrace her but, after a relatively short stay, she disappeared into the changing area, ignoring the media as she went.

Earlier, when a microphone was thrust in front of her, she said tersely. "It's over now, I suppose I just didn't have any energy.

Her father described it as heartbreaking. "After all the hard work she's put in over the last four years, all the good runs she's had in that time, it's difficult to accept I just don't understand," he said.

Those were the sentiments suspect of many Irish supporters, including the handful of Irish Americans who verbally abused the athlete's parents after she had run off the track in the 5,000 metres final.

For those of us who have monitored O'Sullivan's progress since her first major championship appearance in Split in 1990, the underlying cause of this debacle will continue to fuel debate, long after these Games have ended.

She believes that a physical ailment contributed to her defeat last Sunday. But the fact that she chose to jog the seven miles back to her residence from the track to "clear my head", suggests that it was not a major problem.

A second reason even if it runs counter to the evidence of her career to date is that the problem was psychological, rather than physical. Olympian fulfilment is the ultimate goal of every athlete and added to the burden of expectancy, imposed by the public, was the inner pressure which she herself applied.

Speaking after Michelle Smith had won the second of her gold medals, she said. "It's heightened the pressure on me. Michelle has done great and there's no way that I'm going to settle for less."

Those were the sentiments of an athlete desperate to distance herself from the scars of Barcelona four years ago but, as it transpired, they spawned an even bigger, more serious problem.

Over the next few days, O'Sullivan will reflect on her Atlanta disaster, dissecting it piece by piece in the hope that she can came up with something approaching a rational answer.

In the meantime, she must also give some consideration to her immediate engagements on the Grand Prix circuit which still offer her a means of retrieving some self respect.

As things stand she is scheduled to run in meetings in Monte Carlo, Zurich, Cologne, Brussels and Berlin within the next four weeks, but whether she fulfils any, or all, of those commitments in her present state of mind remains unclear.