A statement from Doyle Management, the firm that represents Powell, read: "Asafa Powell has officially withdrawn from the 100m event in Daegu citing a continued groin strain.

"Powell suffered a groin strain in Budapest on July 30 and has had recurring tightness and pain ever since.

"After Budapest, Asafa missed eight days of training before he could attempt to sprint again.

"When he returned to the track he was able to sprint but it caused the groin to flare up.

"He has received all sorts of treatments over the past two weeks in the hope of being prepared to run the 100m here in Daegu but today Asafa made the final decision not to run.

"He feels he would not be at 100 per cent and may have trouble coming back after each round.

"Asafa is very disappointed to say the least.

"He was really hoping to be able to run in what was going to be one of the most anticipated races of the Championships.

"He is still optimistic to be able to run the [4x100m] relay."

Powell, the former 100m world record holder and bronze medallist in the event at the 2007 and 2009 World Championships, was the fastest man this season at 9.78sec.

Bolt, who dismissed a suggestion that he was also carrying an injury, said he was "not in 9.5 shape" but that he was focused on retaining his titles.

Asked about the absence of Powell from the 100m, which starts on Saturday (August 27), Bolt responded: "This is the first I've heard about it.

"I can't answer that question.

"I saw Asafa yesterday so I don't know."

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