Who will be the new sprint king in Doha?
On the evening of Saturday 28 September, all eyes will be on Doha's Khalifa International Stadium.
The title at stake is one of the most prestigious in athletics and indeed all of sport - that of the fastest runner in the world.
Coleman has the best time in the world this year, 9.81s recorded at the Prefontaine Classic at the end of June, but he recently escaped suspension after being charged by the US Anti-Doping Agency (USADA).
The defending champion
Justin Gatlin won his second 100m world title in 2017, 12 years after his first.
The Olympic champion from Athens 2004 is now 37 years old, but won't give up his crown without a fight.
When it comes to peaking for the big occasion, few have been more consistent than Gatlin who spent most of the past decade chasing a certain long-legged Jamaican.
He suffered a setback at the start of September when he pulled up with what appeared to be a hamstring pull in Zagreb.
But tests showed no damage and he was soon back in training
We caught up with Gatlin in July in Lausanne where he ran 9.92s just a few days after clocking 9.87s in defeat to Coleman at the Prefontaine Classic.
He might have more than a few miles on the clock, but he is still a force to be reckoned with.
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Coleman bids to make amends
Before August, Christian Coleman was looking like the hot favourite to go one better than two years ago and claim the world 100m title.
With his great rival Noah Lyles opting to stick to the 200m, Coleman's victory over Gatlin in Stanford, the temporary home of the Prefontaine Classic, marked him out as the one to beat.
At the end of July, he cemented that status with victory in the US Track and Field Championships 100m from Mike Rodgers and Christopher Belcher.
But a dark cloud moved over his World Championship hopes three weeks later as reports emerged claiming the 23-year-old had three 'whereabouts failures' in the space of a year, a scenario which would normally result in a two-year suspension.
The first of these failures was recorded by the US Anti-Doping Agency (USADA) as a filing failure - where an athletes does not make "an accurate or complete" disclosure of where he or she can be located - on 6 June 2018.
Unlike a missed test, a filing failure is backdated to the start of the testing quarter, in this case, 1 April 2018.
With the third of the transgressions taking place on 26 April 2019, that meant Coleman had committed just two whereabouts failures within 12 months leaving him clear to run.
The Atlanta-born sprinter will double up in Doha having finished second to Lyles in the 200m.
But the 100m represents his best chance of a first global outdoor title.
The big-name absentee
Noah Lyles has opted to stick to his plan made at the start of the season to only run the 200m in Doha.
While his clash with Christian Coleman over half a lap should be something to savour, the sight of the two closely-matched sprinters going head to head over 100m would have been one to behold.
However, Lyles does plan to double up in Tokyo as he bids to succeed Usain Bolt as the king of world sprinting.
The African challenge
With Lyles out, the biggest threat to the gold and silver medallists from 2017 looks to come from Africa.
Nigeria's Divine Oduduru and Akani Simbine of South Africa both made their Olympic debuts at Rio 2016 with Simbine finishing fifth in the 100m final.
Oduduru went out in the semi-finals of the 200m, but his performances this season have made the world sit up and take notice.
In June's NCAA Championships held in Austin, Texas, the 22-year-old Texas Tech University student won the 100m in a personal best of 9.86s
That equalled the time set by Lyles and Coleman at the Shanghai Diamond League for the fastest in the world this year with Coleman subsequently going quicker in Oslo and then at the Prefontaine Classic.
Just 45 minutes later, Oduduru retained his 200m title in a new Nigerian record of 19.73s.
Speaking exclusively to Olympic Channel, the Delta State native said talking to Usain Bolt at Rio 2016, and seeing the likes of Coleman and Lyles on the American college circuit, has helped him get to where he is now.
And he is confident that he will be standing on the podium in Doha.
"That is one thing I'm working towards. I believe it's going to be my first World Championships, and it's going to be first one I'm going to get a medal at.
"Everybody's good, everybody's fast, everybody's going what they need to do but... I know. It's going to be a moment to remember. I'm going there not just to register my presence, I'm going there to do something different." - Divine Oduduru
Oduduru took silver at last month's African Games in Rabat but he is making sure he is fully primed and ready to challenge for medals in Qatar.
He will be accompanied by compatriot and Florida Gators college star Raymond Ekevwo.
The 20-year-old broke 10 seconds for the first time in winning the African Games title in Rabat, beating Ivorian sprinter and pre-race favourite Arthur Gue Cisse.
With this being an unusually long season in track and field, some athletes may have been holding something back for Doha.
That could be the case for Akani Simbine who has only fleetingly shown glimpses of his best in 2019, including at July's London Anniversary Games where he beat Zharnel Hughes and former world champion Yohan Blake with a season's best of 9.93s,
Speaking to Reuters in August, the 25-year-old from Johannesburg said he has nothing to fear from the top Americans:
"I know where they are at. I know toe to toe if they are at their best and I am at my best, it will be a good race.
"I believe I can be the best and if I’m in the sport then I can’t just say, ‘Oh well, Christian is running fast, Noah is running fast, Gatlin is running fast, I can’t beat them’ – then I’m in the sport for the wrong reasons.
"Not a day passes where I don’t dream of holding the gold medal and being the fastest man and just achieving goals that I set for myself and showing the world that a South African boy can be the best in the world." - Akani Simbine
De Grasse seeks improvement
After an injury-ravaged couple of years, Andre De Grasse is gradually returning to the form which won him three medals at Rio 2016 including bronze in the 100m.
The Canadian told CBC he takes nutrition, sleep and recovery more seriously now after sustaining a hamstring injury ahead of the 2017 World Championships which dogged him for the next 18 months.
He said, "I'm not eating out as much or snacking on junk food. I had to sacrifice some things and not be out late so I was ready for the next training day."
After clocking 9.97s in Berlin at the start of September, he hopes to progress further in Doha.
"All my starts this season have been shaky and I haven't been able to get out with the field, but I was able to get out of the [starting] blocks well and maintain my speed.
"I just have to stay patient and when I hear the gun just react and push. If I do that, I'll be in the mix." - Andre De Grasse
With Bolt now enjoying retirement, 2011 world champion Yohan Blake leads Jamaica's challenge.
The 29-year-old has a best of 9.96s this season, set at June's Jamaican Championships, one of three sub-10 runs in 2019.
Last year's European champion Zharnel Hughes, a former training partner of Usain Bolt, has ducked under 10 seconds four times this year.
But the Anguilla-born sprinter was only third in the British Championships and would need to step up markedly on recent performances to be in with a chance of a medal.
Japan's Abdul Hakim Sani Brown finished third in the NCAA Championships behind Ododuru, setting a new national record of 9.97s in the process.
The University of Florida student won two golds at the 2015 World Youth Championships, and he will be hoping for a final berth before setting his sights on competing at a home Olympics in Tokyo next year.
Japan actually boast three sub-10 sprinters in their squad with former national record holder Yoshihide Kiryu and 2018 Asian Games champion Yuki Koike completing the trio with their relay squad one to look out for after taking silver at Rio 2016.