Defending champion and 800m world record holder Kenya's David Rudisha has withdrawn from next month's IAAF World Athletics Championships with an injury.
The championships are billed for 4 August to 13 August in London, the United Kingdom.
"Its sad and disappointing to announce my no show in the forthcoming #london2017 WC due to a quad muscle strain," Rudisha, 28, tweeted on Monday.
Rudisha set the 800m world record of 1 minute 40.91 seconds five years ago in London as he won Olympic gold and would have been gunning for a third straight gold medal at the World Athletics Championships.
In Rudisha's absence, his compatriot Emmanuel Korir and Botswana's Nijel Amos will be favourites for the 800m men's gold in London.