The former 100 metres world record holder Asafa Powell withdrew from this week's London Diamond League meeting with a back and hamstring strain.
The Jamaican, whose 100 metres duel with Tyson Gay was to be one of the highlights of the event, is suffering with the same injury that forced him out of the Stockholm meeting last week.
Powell's withdrawal, who held the 100 metres world record for three years until Usain Bolt smashed it in 2008, is a blow to organisers who had hoped to stage a showdown between Powell, Gay and Olympic and world champion Bolt.
Bolt declined to enter because of tax reasons and has since been ruled out for the season with injury.
Gay's main rival in London will now be fellow American Walter Dix, the Olympic bronze medallist.
