Wilson Kipsang is aiming to regain the world record at the Berlin Marathon on Sunday, but will face stiff competition from fellow Kenyan Emmanuel Matai.
Kipsang broke new ground with a time of two hours, three minutes and 23 seconds to triumph in the German capital in 2013, and he added victories in London and New York the following year.
However, Dennis Kimetto broke his record by 26 seconds in Berlin in 2014 - the third time a new world record had been clocked in four Berlin Marathons - and Kipsang is desperate to go faster.
He said: "I've trained well and, three years down the line from my world record here, I feel good and believe I have the potential to attempt the world record once more.
"Running at the top level, there is a lot of wear and tear on the body, especially when you are running for a time, but I am very focused on the world record."
Kipsang is not the fastest man in the field, though, with Mutai possessing that honour.
He produced a personal best of two hours, three minutes and 13 seconds on the streets of Berlin when he finished second to Kimetto in 2014, and his eyes will be firmly on first place this time around.
Kenenisa Bekele of Ethiopia, a three-time Olympic gold medallist on the track, will be hoping to spring a surprise despite being yet to clock a time below two hours and five minutes, with countryman Tsegaye Mekonnen also one to watch.
In the women's race, Aberu Kebede will be aiming to complete a hat-trick of Berlin Marathon victories.
The Ethiopian is the fastest female in the field and primed to add to her successes in 2010 and 2012, having finished second in her only other appearance last year.
Kedebe can expect a battle from compatriots Amane Beriso, second in Dubai in January, Birhane Dibaba and Ruti Aga.