Paula Radcliffe will reassess her racing schedule after announcing that she is to miss this month's Flora London Marathon because of a foot injury.
Radcliffe, who returned early from her training base in America 10 days ago for expert treatment, left it to the last possible moment before making her decision.
The world marathon record-holder has been troubled by the same problem which forced her out of last month's Commonwealth Games 10,000 metres.
She came came back from Albuqerque, New Mexico, to receive a week's treatment from top German surgeon Hans Muller-Wohlfahrt in Munich.
It is understood the injury - a knock-on effect after she bruised the underside of a toe on a training run last December - will not entail a long absence. Bone bruising can take months to settle, and rest may not necessarily help it clear up any faster.
With the London Marathon only 20 days away and boasting a world class field, Radcliffe nonetheless had to accept she would not be in the right shape to chase a fourth title.
The 32-year-old said: "I have worked really hard over the last few months, so it is gutting now not to be able to take part The Flora London Marathon is something that is extremely important to me, and I have done everything possible to resolve the problem and get to the start line.
"I have to accept that it needs a short period of total rest and I also have to focus on moving on from this and my future. I am really disappointed to have to miss this year's event."
Radcliffe, who produced a world-record time of two hours 15minutes and 25 seconds when she won in 2003, makes no secret of the fact the London race is her favourite.
It seems most likely, however, she will have to wait until August before she is ready to race again - in defence of her European Championship 10,000m title.
She could then contest an autumn marathon, with Chicago and New York obvious contenders. Radcliffe was not the only one to announce her London absence today.
British number one Jon Brown, sixth last year in a personal best 2:09:31, had a similar tale to tell.
"I have been suffering from a foot problem recently which is clearing now but has left me way behind in my training preparations for London," he said.
"I feel like I have only done two-thirds of the training needed. I know this isn't enough for London and I cannot expect to perform to the level I feel I should.