Everything you need to know about the Chicago Marathon
There's little doubt that the marathon is the hottest athletics event on the planet right now.
It could be a historic weekend for Kenya with Kosgei aiming to break Mary Keitany's women-only world record and Paula Radcliffe's mark with male pacemakers from 2003, both set in London.
Chicago is the first stop in the new Abbott World Marathon Majors season although results from the recent IAAF World Championships in Doha will count towards the final standings.
In the wheelchair events, Manuela Schaer bids for her eighth consecutive World Marathon Major triumph after sweeping the board last season, with Daniel Romanchuk also aiming for back-to-back wins in the Windy City.
And you can watch the action live on Olympic Channel (geo-restrictions may apply).
Farah's recovery mission
Mo Farah had hoped to challenge Kipchoge at April's London Marathon.
But the four-time Olympic track gold medallist finished down in fifth place, three minutes behind the world record holder.
On his London setback, he told SI.com, "It’s important to me in that marathon to just run my own race rather than get carried away. For me, even though I’ve run 2:05, I was still overall disappointed with that position and time. I believe if things had gone well, I could’ve gone faster.
After hinting that he might defend his world 10,000m title in Doha, the Briton opted to stick to the road and return to the scene of his first marathon victory.
He warmed up with his sixth consecutive Great North Run half-marathon victory last month and, without Kipchoge in the field, hopes to return to winning ways.
Farah will face three men with faster personal bests than his 2:05:11 recorded in claiming last year's race.
Lawrence Cherono poses perhaps the biggest threat after his win in April's Boston Marathon.
That performance looks even better now with the man he beat in a sprint to the line, Lelisa Desisa, going on to become world champion last week in Doha.
Dickson Chumba is another Kenyan hoping to come out on top in Chicago.
The 32-year-old set his personal best of 2:04:32 in taking the 2014 edition, but failed to complete last year's race.
In 2019, he was a distant third in March's Tokyo Marathon behind Ethiopia's Birhanu Legese.
Seifu Tura was a late addition to the field with the 22-year-old boasting victories in Milan and Shanghai last year.
The Ethiopian has a personal best of 2:04:44 from his seventh in Dubai at the start of 2018, but failed to finish in Tokyo on his last marathon outing.
Kosgei chases history
Brigid Kosgei has established herself as one of the world's leading female road runners with four wins in eight marathons.
The 25-year-old was second in the 2017 Chicago Marathon and the 2018 London Marathon before going one better in both races in impressive times.
Immediately after her London victory in April, she said she would be going to Chicago to defend her crown rather than go for the World Championships.
The Kenyan is clearly in excellent form having run 1:04:28 - the fastest half-marathon in history - to take last month's Great North Run although the course layout meant it could not count as a world record.
That preparation gives her a chance of improving on her personal best of 2:18:20 set in London and threatening Mary Keitany's 2017 world record of 2:17:01.
She could even come close to Paula Radcliffe's 2003 mark of 2:15:25 achieved with male pacemakers.
Tokyo 2020 is definitely in her thoughts, but Chicago is her immediate focus.
"I would like to compete in the Olympics but there are hurdles to be cleared before thinking of the Olympics. For now, winning in Chicago will be important and then we will see how 2020 turns out" - Brigid Kosgei as reported by Xinhua
Kosgei's biggest danger will almost certainly be world number six Gelete Burka.
The Ethiopian has won her last two marathons, following up her Ottawa victory in May last year by taking this April's Paris Marathon.
Only Kosgei has a better personal best than Burka's 2:20:45, and it looks like these two will end up battling out the closing stages.
Schaer aims to continue dominance
Manuela Schaer has been in a class of her own for the past year.
The Swiss has won every major race since Berlin in September 2018 with her unbeaten run currently standing at seven.
When she retained her Berlin crown last month, Schaer completed a unique season Grand Slam of the six Marathon Majors.
Schaer - a three-time Paralympic Games medallist on the track - will be expected to take her winning streak to eight when she defends her Chicago Marathon title on Sunday.
She won't be able to afford to let her level drop, however, with three-time winner Amanda McGrory and eight-time champion Tatyana McFadden - Schaer's nearest competitor in the past couple of years - leading a strong home challenge and Australia's Madison De Rozario hoping to go one better than her second place last year.
Daniel Romanchuk returns to the scene of his first Marathon Major victory with the young American now firmly established as the man to beat.
The 21-year-old from Maryland took four wins out of six to take the overall title last season, starting off by edging out Marcel Hug in Chicago 12 months ago.
Four-time winner Josh George and 2013 victor Ernst van Dyk look set to provide his biggest threats with veteran David Weir, runner-up in Berlin last month, also vying for a podium finish.