EUGENE, Ore. :Britain's Max Burgin, the fastest man in the world this year and a real medal hope for the men's 800 metres, withdrew from the first round heats shortly before they got underway on Wednesday because of an injury, UK Athletics said in a statement.
Burgin, 20, posted his world lead of one minute 43.52 in Finland last month and as a noted front-runner had been hoping to complete a middle distance double for Britain after Jake Wightman won the 1,500 metres on Tuesday.
In his absence Olympic champion Emmanuel Korir of Kenya looks an even stronger favourite and he advanced safely, as did his in-form compatriot Wyclife Kinyamal and Canadian Marco Arop, who had the fastest time of the day.
"The race was not perfect because of the heat, I did not want to struggle too much," said Korir, who barely broke a sweat in winning a pedestrian opening heat.
"After the Olympics, it was not easy. It takes time, training, lot of stuff going on there but at least I am here and that is what matters."
American defending champion Donavan Brazier, troubled by a foot injury in recent weeks and awaiting surgery, was way off the pace in his heat and failed to progress. Tokyo Olympic bronze medallist Patryk Dobek of Poland also missed out.
The semi-finals are on Thursday with the final one of the highlights of a packed Saturday night session.