Eliud Kipchoge is without doubt the greatest marathon runner on the planet.
But his training partner, Geoffrey Kamworor, has strong claims to be number two.
Kamworor watched on TV as a 10-year-old when Kipchoge won the world 5,000m title in 2003.
And speaking to Runner's World ahead of his NYC Marathon title defence on Sunday, he says Kipchoge has been a continual source of inspiration.
"I was optimistic that at one point I would see him in real life. The reality came true."
In 2011, Kamworor started to train under 1992 steeplechase silver medallist Patrick Sang in Kaptagat with Kipchoge quickly becoming a major influence.
"He always tells us to take our career seriously, to focus and be disciplined. Eliud is a simple, disciplined guy—hardworking, focused, and he respects athletics. He values his career, his talent.”
While Kamworor's first marathon completion came back in 2012 - finishing third in Berlin in what remains a personal best of 2:06:12 - he soon excelled over shorter trips.
The 25-year-old is the defending three-time world half marathon champion, including victory over four-time Olympic champion Mo Farah in Cardiff in 2016.
Kamworor has also won the last two World Cross Country Championships titles, wearing Kipchoge's running spikes to retain his crown last year.
And his mentor was at the finish in Central Park 12 months ago to celebrate Kamworor's first victory over the 42.195km distance.
The latest Kenyan running star is favourite to retain his title with last year's third, Abdi Abdirahman, and fifth, Shedrick Biwott, reopposing.
Two-time Olympic medallist Bernard Lagat makes his marathon debut at the age of 43.
Like Kipchoge, Lagat is a former 5,000m world champion - he also won gold over 1500m in 2007 - and he says he should perhaps have switched to the roads sooner.
Lagat said, "I wish I had done it way earlier, but then I was also thinking to myself I want to be able to run at the highest level still on the track.
"When I stopped running track in 2016, I used 2017 as a way to get me ready mentally, do a few races, do 10ks, do 5ks, and also the half-marathon, to make sure that when I say I want to do my first marathon. I will be making it a serious attempt."
Flanagan faces rivals from home and abroad
Shalane Flanagan became the first home winner for 40 years of the women's NYC Marathon 12 months ago.
The Oregon-based runner had suggested she would retire after claiming her first major marathon victory in the Big Apple, but the lure of defending the title has proved too great to resist.
Retaining the title will be far from easy, however, with London Marathon winner and Olympic 5,000m champion Vivian Cheruiyot heading her rivals.
Cheriuyot's fellow Kenyan, three-time winner Mary Keitany, is back to try to regain her crown while Flanagan's compatriot Des Linden is bidding to complete a rare Boston-New York City marathon double in the same year.