London - A 12th world title beckons for Jamaican sprint star Usain Bolt when he takes to the track in London on Saturday to defend his 100m crown. 

Bolt, 30, will bring down the curtain on his glittering career at the end of this season, leaving a gaping hole at the heart of track and field built as much around his charismatic personality as his accolades. 

And his trophy haul is nothing short of miraculous: 11 world and eight Olympic gold medals, 13 of which have come in individual events. 

Apart from a false start in the 100m at the Daegu world championships in 2011, Bolt has made the blue riband event his own since winning at the Beijing Olympics in 2008. 

His world-record setting victory at the Berlin champs a year later was the first of three world wins along with Moscow 2013 and Beijing 2015, peppered by Olympic golds in London 2012 and Rio 2016. 

"You won't be particularly surprised when I say I'm sad he's going," IAAF president Sebastian Coe said this week. 

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

Bolt was made to work in Friday's first round, blaming the "worst ever" starting blocks for a botched opening half before he turned on the afterburners to settle everyone's nerves. 

"That was very bad," Bolt said. "I'm not fond of these blocks. 

"I have to get this start together because I can't keep doing this. It's shaky." 

Bolt will race in the third and final semi-final, scheduled at 1819 GMT, with the final slated for 21:45. 

The Jamaican will be up against American Christian Coleman, the world's fastest over 100m this year with 9.82sec, in his semi-final. 

But he avoids Coleman's veteran teammate and his arch-rival Justin Gatlin, who races in the first semi alongside Bolt's compatriot Julian Forte, the sole sprinter to dip under 10sec in qualification with a 9.99. 

Gatlin was afforded a rough reception on Friday, loud boos and jeering ringing around the same stadium where in 2012, his rivalry with Bolt was presented as 'good against evil', given the American's doping-tainted past. 

Gatlin, the last man to beat Bolt over 100m - by a hundredth of a second in Rome in 2013 - said he was focused on himself. 

"I'm not worried about the crowds. I just focus on my start and my race," said Gatlin, silver medallist behind Bolt at the last two world champs, having also picked up a silver and bronze at the last two Olympics to go with his 2004 gold. 

In eight individual finals at the past four worlds (as well as in four 4x100m relay finals), Bolt has only suffered one that one hiccup in Daegu and it would be a brave person to bet against the Jamaican adding to his honours. 

Even Gatlin conceded that "Bolt looks good". 

"He has his long legs so is not out of blocks very fast but he keeps the energy very well so that is going to count in the end."