With Olympic qualification at stake, the championships have naturally drawn remarkably strong fields.
The 73-strong men's line-up includes the London Olympic champion Ous Mellouli (Tunisia), current World Cup leader Jack Burnell (Great Britain), last year's overall series winner Allan do Carmo (Brazil) and defending world champion Spyridon Gianniotis (Greece).
Radford has prepared with two World Cup races and he will be hoping it is a much cleaner race on Monday after suffering cuts to his eye and a sprained finger after an over-physical race at the recent World University Games in Korea where he finished eighth.
The Pan Pacific Championship bronze medallist had a 16th and 11th placings in two World Cups in Europe.
The Rotorua swimmer has also been selected as the flagbearer for the New Zealand team for the opening ceremony.
There are 61 entered the women's race with favourites including London champion Eva Risztov (Hungary), defending world champion Poliana Okimoto (Brazil), the Olympic medallist and current Pan Pacific winner Haley Anderson (USA), World Cup leaders Ana Marcela Cunha (Brazil) and Rachele Bruni (Italy) and European champion Sharon van Rousendaal (Netherlands).
The course, used for the World University Games two years ago, is in the Kazanka River. The rest of the New Zealand team are in Barcelona, with the pool competition to start on August 2.