Chicago - Mo Farah takes on former training partner and race rival Galen Rupp on Sunday at the Chicago Marathon as the British athletics great continues his quest to establish himself as a force in the ultimate distance event.
Farah, who twice achieved the 5 000m-10 000m Olympic double and also won world titles in both events in 2013 and 2015, will be running in just his third full marathon.
The Somali-born star finished third in London in April, despite twice making a mess of picking up his water bottle at the drink stations.
He's hoping to iron out such technical difficulties as he eyes the European record of 2:05.48 set by Norwegian Sondre Nordstad Moen in Fukuoka in December 2017.
"If I could win a major marathon, it'd be great," Farah told Runner's World.
"I think the aim is to try not to make as many mistakes - like, pick up my drink bottles!
"For me satisfaction will be to run a personal best. Second, if I can't do that, a great result will be a win or mixing with the guys and seeing where it comes up at the end," added Farah, who noted the Chicago field includes several athletes who have clocked 2:04.
That includes Ethiopians Mosinet Geremew (2:04:00) and Birhanu Legese (2:04:15) and Kenyan Dickson Chumba (2:04.32).
Also likely to be in the hunt is Kenyan Abel Kirui, the 2016 champion who was beaten across the line last year by Rupp and compatriot Geoffrey Kirui, who won the Boston Marathon and 2017 World Marathon Championships in 2017.
But the potential showdown between Rupp and Farah, who once trained together in Oregon under Alberto Salazar, is an intriguing story line.
Rupp still trains with Salazar, while Farah has been working with Gary Lough - husband of British star Paula Radcliffe - since switching to road racing a year ago.
"I have never been in such good shape to run so fast," said Rupp, who might well need to better the American record of 2:05:38 - held by Khalid Khannouchi - to win.
The Farah-Rupp duel should benefit from the reintroduction of a pace-setter after three editions without them.
Even so, humid weather with a chance of rain might slow things down in the first major marathon since Kenyan Eliud Kipchoge smashed the world record in Berlin last month with a time of 2:01:39.
The women’s race will see two-time champion Florence Kiplagat of Kenya make her return to competition after dropping out of last year's Chicago Marathon with a muscular injury.
She can expect a strong challenge from compatriot Brigid Kosegi, who finished second last year behind Ethiopia's Tirunesh Dibaba last year.
Ethiopia's Birhane Dibaba, a two-time podium finisher in Chicago, also features in a women's field that includes nine runners who have clocked 2:25 or better.