An unwell Sonia O'Sullivan left many questions unanswered after a disturbing performance at Crystal Palace on Saturday in her last competitive 5,000 metres run before the Olympic Games.

O'Sullivan, a mere shell of the athlete who has captivated crowds over the years, trundled home in ninth place, some 200 metres and 36 seconds adrift of the Ethiopian Ayelech Worku in a time of 15 minutes 17.42 seconds.

For an athlete who confidently expected to run inside her national record of 14:41.50, after what was described as a near perfect training session the previous Tuesday, her defeat on such a comprehensive scale was little short of astonishing.

And her time was put in stark perspective when, at a meeting at Hechtel in Belgium later in the day, Breda Dennehy Willis, Rosemary Ryan and Maria McCambridge all ran faster times to get inside the Olympic "A" standard.

The 5,000 metres is a long, lonely race when you're not going well, and after being dropped on the fourth of the 12-and-a-half laps it may have seemed like a marathon for the Irish woman as she sought in vain to find some kind of spark.

Paula Radcliffe and Tegla Loroupe, who had obviously identified O'Sullivan as the one they all had to beat, quickly read the distress signals and, after running at her shoulder in the early stages, went away from her to give chase to the leaders.

For a woman who has designated the marathon as her objective in Sydney, Loroupe's pace at the shorter distances is incredible and soon she was testing the resolve of the compact Ethiopian.

In some respects Radcliffe, in only her second race since undergoing a knee operation in May, was more impressive still. The style, as ever, was laboured, but there was nothing wrong with either her strength or her courage as she progressed through the field to dispute the lead with the two Africans over the last 1,000 metres.

Sadly, and perhaps inevitably, she didn't have the pace to cope when Worku surged on the last lap for the fastest 5,000 metres time of the season, 14:41.23. But in every other respect it was a convincing display by the Liverpool athlete on her way to the Olympic 10,000 metres championship.

For O'Sullivan, of course, it was a disquieting day not wholly dissimilar to her experience on this same track before setting off for Atlanta four years ago.

Over the years she has played on our emotion as no other Irish sports person. And that perhaps is the enduring fascination of an athlete who in good times and bad has seldom failed to hold the watching public captive.

The effects of a huge training session at Kingston four days earlier, when she ran some 8,000 metres in interval work, aggravated by the fact that she felt unwell on Saturday, were undoubtedly contributory factors to her tired running.

Her medical problems are expected to clear in a matter of days, but the bigger challenge will be to rediscover her self-belief when she goes back to the track for the 3,000 metres in Friday's Grand Prix meeting at Zurich.

"I think the sensible thing is to get back into competition as soon as possible and try and run this race out of my system," she said.

"Maybe it was a reaction to the work I had done the previous Tuesday. I felt a bit tired on the following days but nothing that would have bothered me if I'd been going training on Saturday. But of course it's a lot different when you're running in front of a packed stadium and expected to do well.

"There have been days like this before, of course, and I've got over them. Now I just want to forget it and get on with the job of proving in Sydney that championship competition and Grand Prix running are two very different things."

The Irish champion was in good company: Ato Boldon could finish only fourth in the 100 metres, won by Bruny Surin of Canada; Gabriela Szabo was run out of the finish of the 1,500 metres by her Romanian team-mate Violeta Szekely, and Cathy Freeman didn't even get to the start of the 400 metres, won in some style by the Mexican Ana Guevara.

Nor was it all doom and gloom for the Irish on a day when the extraordinary DCH athlete, Terry McHugh, almost certainly booked his place in the Olympic team with an "A" qualifying standard of 82.75 metres in the javelin.

McHugh was admitted to the competition only as a late entrant, but he seized his unexpected chance to improve by more than a metre on his seasonal best, thrown in Switzerland a week earlier. Now his reward will be a place in the cast for his fourth consecutive Summer Olympics which, added to his two appearances in the Winter Games, puts him in a special category in Irish sport.

It was a rewarding afternoon also for high jumper Brendan Reilly, who upped his best figures of the season to 2.24 metres and was desperately unlucky not to have gone over on his first attempt at 2.28. Russia's Vyacheslav Voronin won the competition with a massive jump of 2.40 metres, the highest in six years.

Ireland will be represented in the Olympic relay championships for the first time in 52 years following the decision of the Olympic Council of Ireland to approve the selection of teams for both men's events and a women's 4x400 metres formation. Maeve Kyle, the distinguished Irish Olympian, has also been added to the list of coaches.