Two Kenyan greats. Two world record attempts. One marathon.
Eliud Kipchoge defends his Berlin Marathon title on Sunday, aiming for his fastest race ever.
But the Olympic champion will not have things his own way.
His main rival is former world record holder Wilson Kipsang, who will be hoping to get the better of his fellow countryman.
Personal best aim
“Berlin, out of the six major marathons, has the fastest course ever, and I think that’s the place to run my personal best,” said Kipchoge.
The Rio 2016 gold medallist won in the German capital in 2015, and again last year in difficult rainy conditions.
“His aim is, of course, a fast time, considering the conditions on the day," his manager Valentijn Trouw underlined.
Kipchoge’s personal best would mean a world record pace.
His best is just eight seconds slower than compatriot Dennis Kimetto who won four years ago in 2:02.57, the record which stands today.
In fact, the last six men's marathon world records have been set in Berlin.
With Kipsang also in the mix, it will be a race against not just the clock but also a long-time rival.
Kipchoge's greatest race?
Since winning in London in April, the 33-year-old has stepped up his workouts.
It’s been an intense four months of training, pushing his legs and his mind ahead of what could be his greatest race ever.
“My legacy will be fully concentrated on (the idea that) 'No human is limited.'" - Eliud Kipchoge
"I actually want to tell every living soul in this world everything he wants to do, he can do, provided he’s believing and trusting in it,” said the three-time London Marathon winner.
Having completed training at Kaptagat in the Kenya's Rift Valley region, Kipchoge is raring to go.
“Eliud has been in good shape several times in the past and he is also now in good shape,” his manager Trouw said.
"After the four-month build-up we believe he is ready for the race.”
Of Kipchoge's last 10 marathon starts, he has won nine with his last defeat coming in the 2013 Berlin Marathon.
On Sunday he will again be the favourite, a tag he has carried for what seems like an eternity.
There are not many athletes who have been at the top of their sport for 15 years.
But as an 18-year-old he outsprinted two track legends, Kenenisa Bekele and Hicham El-Guerrouj, to win the 5000m world title.
Following in Gebrselassie's footsteps
It was Kipsang who handed Kipchoge his last defeat in 2013 as he set the then-world record time in Berlin.
And the London 2012 bronze medallist, three years Kipchoge's senior, acknowledges the task ahead of him is far from straightforward.
"For sure with Eliud in the field it will be a difficult race. But I will be ready," he told KweséESPN. "The world record is on my mind."
If the 36-year-old does regain the record from Kimetto, he will become just the second member of a very exclusive club.
Only Ethiopian legend Haile Gebrselassie has broken the marathon world record more than once.
Few would bet against the record falling again in Berlin, but who will the new mark belong to?