Eight-time Olympic champion Usain Bolt described his performance as “very bad” as he won his 100m heat at the World Championships in 10.07 seconds.
The Jamaican who is retiring after the event in London beat Great Britain’s James Dasaolu into second (10.13) but was frustrated with his start.
“I’m not fond of these blocks,” said Bolt. “I have to get this together.”
The USA’s Justin Gatlin, twice suspended for doping, was booed when he came out to race but eased through.
Britons Reece Prescod (10.03) and Chijindu Ujah (10.07) took top-three spots to reach Saturday’s semi-finals.
Prescod’s mark was a lifetime best and earned him third place in a heat where Jamaica’s Julian Forte produced the fastest time of the night to win in 9.99 seconds.
The British champion said: “My first World Championships I come out with a PB in the first round – I can’t really complain.
“Being in front of a home crowd it’s great, this is what athletics is all about – I loved it.”
Bolt in contrast looked like he needed to work hard through the middle of the race before tapering down and shaking his head after crossing the line.
The 11-time world champion has only run under 10 seconds once this year and in what was his fourth race of 2017 over the distance he has made his own for a decade, he pointed to his starting blocks as a source of frustration.
“It’s shaky because when I did the warm up it [the blocks] pushed back,” he told BBC Sport. “It’s not what I am used to.”