Double Olympic 800 metres champion David Rudisha has pulled out of the IAAF World Championships in London with a quad injury.
The Kenyan, who also took world gold in 2011 and 2015, was bidding to make a triumphant return to the scene of his maiden Olympic triumph but confirmed on Twitter that he will not compete.
"It's sad and disappointing to announce my no show in the forthcoming #london2017 WC due to a quad muscle strain," he wrote.
Rudisha shot to global prominence in 2012 when he broke his own 800m world record to win Olympic gold at London Stadium, becoming the first man to go under one minute and 41 seconds as he clocked 1:40.91.
Four years later, in Rio de Janeiro, Rudisha was the first man since 1964 to retain the men's 800m title, but he had been expected to face stiff competition from Emmanuel Korir and Nijel Amos for gold this time around.
The World Championships begin on Friday, with the men's 800m heats scheduled for the following day.