It sets up a mouth-watering Friday final with fellow American Kenny Bednarek and Jamaican Bryan Levell, who were similarly impressive but, unlike Lyles who ran hard through the line, turned the burners off 50 metres out.
Lyles, third in the 100m on Sunday after a delayed start to his season, looked relaxed on the start line of his preferred event, as a cool breeze and light drizzle made conditions much more gentle than in the oppressive previous days.
Going in the third of three heats, he clearly decided that he wanted to lay down a marker – and get the best final lane – by going out hard.
"I surprised myself," Lyles said. "I kind of backed up a little bit as we got to the last 20 metres but I'm going to put on a whole race in the final.
"When I got up after the first 50 metres, I thought I heard Zharnel (Hughes of Britain) running along and I said to myself, 'You ain't catching me'. The message today was that they can't beat me.
"I knew I was running fast when I exited the curve but I didn't expect 19.51. I was expecting 19.60 or 19.70. Don't miss the final, it's going to be magical."
Bednarek fuelled by anger
Bednarek is fuelling himself on the anger of finishing fourth in the 100 after qualifying so well. With two Olympic 200m silvers and another from the 2022 world championships, he is well overdue an appearance on the top step.
Bednarek’s run was a carbon copy of his heat as he blasted the bend then settled for a controlled cruise home to clock 19.88, a tenth faster than in the heat.
Despite the impressive showings by the US duo, Levell will go into the final oozing confidence that he can complete a Jamaican sprint double after Oblique Seville’s 100m victory.
The last time they achieved that was the last of Usain Bolt’s doubles in 2015, and Jamaica have not managed a medal of any colour in the four championships since.
Levell, third fastest in the field via his 19.69 in Budapest last month, also ran a devastating bend and, despite easing through the last 70 metres, clocked 19.78.
Following him home in 19.95 was Botswana’s Olympic champion Letsile Tebogo, also desperate to make up for his 100m experience after he was disqualified for a false start in the final.
Australia’s 17-year-old hope Gout Gout, appearing in his first major championship, managed only 20.36 for fourth place in his heat and failed to progress.
