World-record holder Paul Tergat says he is devastated that injury has forced him out of Sunday's London Marathon.
Tergat had been among the favourites to win Sunday's race
The 36-year-old, who has yet to win London's prestigious race, had been among the favourites for victory.
But he sustained a calf injury on Monday and misses what would have been his fifth London Marathon.
Tergat told BBC Sport: "This is the most frustrated I have been in my career. I was calling this the race of the century."
He added: "It's very rare to find the quality of athletes you find here. I'd focused so much on this race.
"I was ready for the race. I had done everything possible to make sure I competed in a race like this.
"I tried everything to be able to compete here, but time was against me."
Race director David Bedford told BBC Sport in January he had assembled the finest men's field in the history of marathon running.
Tergat had been due to go head-to-head against double Olympic champion Haile Gebrselassie and had said it would be a "dream" to race against the Ethiopian again.
Olympic marathon champion Stefano Baldini, world champion Jaouad Gharib and 2005 London winner Martin Lel are also in the field.
Tergat said: "What shocked me is how late it came. I was due to fly to London on Wednesday and this problem only came on Monday.
"I trained really well all day, felt fine when I trained in the evening and went to sleep. In the morning I woke up with a lot of pain.
"I tried to train but I couldn't walk afterwards. I flew to Italy to get some treatment and therapy but it didn't work.
"There was no indication of anything wrong in training - I'd had my best period of training ever."
The Kenyan is the second high-profile runner to withdraw from the event after Paula Radcliffe pulled out with a leg injury.
Tergat has been in good form already this season having won the New York Marathon last November after a nail-biting sprint finish with Hendrick Ramaala.