Women's defending champion Brigid Kosgei is the person to beat as compatriots Lawrence Cherono, Dickson Chumba and Bedan Karoki take the battle to Briton Mo Farah when Chicago Marathon goes down on Sunday.
Kosgei claimed her first World Marathon Majors (WMM) victory when she won in Chicago last year in 2:18:30 and would then improve on her personal best when winning in London six months ago in 2:18:20.
Besides becoming the 10th Kenyan woman to win in London, her time made her the seventh fastest time in history hence clear favourite heading into Chicago.
Chicago is the place where the 25-year-old Kosgei made her WMM debut in 2017, finishing second in 2:20:22 behind Ethiopia's Tirunesh Dibaba in 2:18:30.
Come 2018 London and Kosgei settled second again in 2:20:13, losing the battle to compatriot Vivian Cheruiyot in 2:18:31. Her second return to Chicago last year yielded first place.
Last month, Kosgei hit the world headlines again when she chalked the fastest time in half marathon when winning the Great North Run in 1:04:28 in Britain.
While the time was enough to set a new world half marathon record, the course wasn't certified and rated by IAAF. The world half marathon record time of 1:04:51 is currently held by compatriot Joyciline Jepkosgei, which she clocked during the Valencia Half Marathon in 2017.
Kosgei faces compatriot and Paris Marathon champion Betsy Saina as well as American marathon record holder Jordan Hasay. Also in the exciting set up are 2018 US marathon champion, Emma Bates, Mexican national record holder Madai Perez and three-time Olympian Lisa Weightman.
It will be Saina's sixth career marathon but second this season having finished 10th in Boston Marathon in 2:30:32 in April, a race won by Ethiopian Worknesh Degefa in 2:23:31.
Farah is fast establishing himself in marathon since his debut last year in London where he came third in a time of 2:06:22, comfortably beating the British record of 2:07:13 set by Steve Jones in 1985.
He would then win Chicago, bettering his British record in 2:05:11.
However, Farah, the four-time Olympic gold medallist, faces a star-studded filed that includes Cherono, the 2019 Boston Marathon champion and Chumba, who in in Chicago in 2015 in personal best 2:05:30 besides finishing third in 2014 and second in 2016.
On paper, Chumba, who also won in Tokyo in 2014 and last year, looks favourite by virtue of his rich marathon history with Sunday's Chicago being his 24th career marathon outing.
Karoki, who is making his seventh marathon outing, having finished third in Tokyo in March this year, and 2017 Chicago Marathon champion, Galen Rupp are other top contenders.