Usain Bolt kicks off the defence of his world 100m on Friday in his swansong season, the first step to bringing down the curtain on his glittering career.

Bolt, dubbed an "extraordinary competitor" by IAAF president Sebastian Coe, will take to the track in London as favourite for the blue riband event, having won eight individual finals at the past four worlds as well as in four 4x100m relay finals.

The 30-year-old Jamaican has only suffered one hiccup: when he false started in the 100m final in Daegu in 2011.

"That's not going to happen this time," joked Bolt, who also has eight Olympic golds to his name.

"If I show up at a championships I'm fully confident."

Coe heaped praise on the Jamaican on Thursday, but said he remained optimistic for track and field in the post-Bolt era.

"You won't be particularly surprised when I say I'm sad he's going," said Coe, who won two Olympic 1500m gold medals for Britain.

"I'm an athletics fan, I take my federation hat off, the guy has been a sensation.

"He's connected in a way that few, in or out of their sport, have connected. I can't think of someone who's connected that way really since Muhammad Ali."

Coe added: "There's no conjecture, he's the best sprinter of all time, the record books show that.

"But what we're going to miss is not so much the fact that it's unlikely for the forseeable future that someone's going to win three Olympic titles in a row in the 100 and 200, relay, or a sackful of world medals, or world records, it's just that the guy has a personality.

"When we're sitting here with the slightly pre-packaged sports stars that have to look left or right to be able to answer a question most of the time and are nervous, he has a view, he has an opinion and that's what we'll miss."

- Coe optimistic for athletics -

Coe also tried to relativise the absence of Bolt from the world of athletics.

"If we'd be sitting here 15, 16 years ago we'd probably be having the same discussions about the imminent retirement of Michael Johnson or Marie-Jose Perec," the Briton said.

"Athletes came through. Muhammad Ali retired, great boxers came through. You didn't replace Ali but the sport didn't suddenly die so I'm very optimistic about the sport.

"He's committed to staying and helping us engage in all those areas and those discussions will take place once these championships are out the way."

Another potential star of the world champs will be on show Friday: Mo Farah will be aiming for a 10th consecutive global title when he races the sole final of the night, the 10,000m.

The 34-year-old Somalia-born Briton, who will switch his focus to road running at the season's end, has shunned media in the run up to the worlds in a bid to avoid tricky questions about his coach Alberto Salazar and doping claims, since proved to be false.

Friday's session also features qualifying in the men's discus throw and long jump, and women's pole vault and 1500m.