Reigning champion David Rudisha sounded an ominous warning to his 800 metre rivals after winning his heat at Rio 2016 on Friday.
The Kenyan, who took gold in London four years ago with a world record time, looked comfortable as he clocked one minute and 45.09 seconds.
"I'm in good form. There's no doubt about that and I think I'm very confident because I'm finding my power of finishing, the last 100 [metres]," said Rudisha, who regained the world title in 2015. "So I think I'm in a position to control [the races] again.
"Between last year and this year there is a huge difference. I feel like I'm in better form now. Better, almost close to my body in the years 2010-2012. I've never felt as good as in previous years, since I got injured.
"There's a lot of pressure, of course, coming here as a defending champion, as a world record holder, as a world champion.
"There's a lot of expectations, but I'm doing my best, that's all I can say."