A tearful Paula Radcliffe has revealed she has no idea what went wrong in her failed bid for Olympic marathon gold.
The Briton said fans deserved an explanation but was waiting for test results from a Monday medical, adding: "I feel I've let everyone down."
She refused to blame the hot Athens weather for her demise, but admitted: "I felt there was nothing in my legs."
And Radcliffe would not be rushed on a decision to run in Friday's 10,000m, for which she is eligible.
"My plan was to win the marathon and decide after that," the 30-year-old told BBC Sport in an emotional interview.
"It's not a decision I'm going to make for 24 hours because emotionally and physically I need to give it a couple of days.
"I definitely want to get out there to redeem something for all the work I've put in and all the support I've had.
"But I won't put myself into that arena if I'm not right."
Radcliffe, who was watched by 10.7m on BBC One during the marathon, said she had trained for the Greek weather.
"I can't use the conditions as an excuse because they were the same for everyone," she said.
"At the start, I didn't feel too bad. I didn't feel the conditions were bothering me and the same at the beginning of the hills.
"But then just after 15-20km, I felt there was nothing in my legs. At the end I was struggling to stay on the road."
Marathons usually start in the early morning and there have been accusations that the race's schedule was designed to fit in with US broadcasters.
Radcliffe had been among a group of athletes who had campaigned for the race to begin at 0600.
But officials said that the timing was "a joint decision by organisers Athoc, the International Association of Athletics Federations and the International Olympic Committee".
"The athletes were aware of conditions," said Athoc spokesman Michalis Zacharatos, who added there were no plans to revise the timing of the men's race, which is set to start at 1800 next Sunday.
Radcliffe, meanwhile, is looking for answers for her failure.
"You go through bad stages in a marathon, but never as bad as that," she said.
"I've never before not been able to finish and I'm desperately trying to find a reason for what happened.
"I just feel numb - this is something I worked so hard for."