Bolt finished in 19.78 sec, the fastest time of the year. De Grasse was second, just 0.02 sec behind. But the last 20 metres of the race the pair were focused more on talking to each other than anything else.
“He was supposed to slow down. I said, ‘What are you doing, it’s a semi-final?’ That was really unnecessary,” Bolt said after the race.
“I don’t know what he was trying to do but he’s a young kid, he’s great.”
The hugely likeable De Grasse, meanwhile, said he was merely enjoying himself.
“Racing the fastest man in the world, ever, and Justin Gatlin, these guys are spectacular. I’m speechless. They’re probably jumping up and down screaming back home in Canada.
The big surprise was that Gatlin, who has been struggling with an ankle injury all year, failed to qualify for the final having been run out of his heat in fourth.
“My ankle is giving me a lot of problems,” said the American, who still hopes to be able to compete in the 4x100m relays.
“I can’t run properly and I had a tight turn in lane three.”
Bolt, meanwhile, knows he will have to go faster – and what’s more he believes he will.
“I definitely think I can try for my world record of 19.19 sec, I definitely feel that,” he said.
“I need to run efficiently and get into the straight and run the perfect race. I will be hoping for lane six, or seven maybe, to be able to run as smooth as I can.”
Britain’s Adam Gemili also went through as a fastest loser after running 20.08 sec behind Bolt and De Grasse but Danny Talbot and Nathaneel Mitchell-Blake, who both ran 20.25 sec in their semi-finals failed to make it.
“It was a tough watch waiting for that last heat but I’m happy to have made the final,” said Gemili.
“I thought I ran a good bend I came off it level but then I started tightening up badly so those guys got into their running and I didn’t. But hopefully I can get myself in the mix because there were some big names that went out in that third semi-final, so I’m OK, I’m good.
“It’s always open as long as you run your own race and that’s something I didn’t do there. I really tightened up – I’m in a lot better shape than 20.08 – I was really disappointed seeing that. But that’s a good thing I suppose that I’m not satisfied with that and I will go and push on. I’ll probably not get the best lane but I’ll make it work.