Winsbury (33), a physiotherapy student at the University of Otago, represented Australia at two world mountain running championships before beginning his study in Dunedin three years ago.
He is coached by Dick Telford, of the Australian Institute of Sport. Last year's race over the 60km course was won by Martin Lukes (Canterbury) from Winsbury.
Tony Fattorini (Sydney) was third. All three are competing again.
There are 407 competitors in the event, including 45 from Otago and 100 from overseas.
Winsbury was sixth in 2006 and was runner-up last year, when on his honeymoon. His wife Allison is competing in the women's section of the race.
Lukes won the event in his sixth attempt last year after finishing second in four of his previous five races.
Fattorini is hoping to lift himself up from the third placings he has held in the past two years,An overseas competitor worth watching is Hiroki Ishikawa (Japan) who is one of the top trail runners in the world.
He is confident of completing the event in a record time of 4hr 30min. The record is held by Canterbury distance runner Phil Costley, who won the race in 4hr 37min 41sec in 2005.
Costley is confining himself to the shorter Luxmore Grunt this year.
Chigaya Mase (Japan), the women's winner last year, will be challenged by runner-up Lara Prince (Canterbury) and fourth placed Laura Beaumont (Porirua).
Another international in the field is Vanessa Haverd (Canberra) who was second at the Australian mountain running championships. The women's record of 5hr 23min 34sec was run by Zelah Morral in 2003.
A race within the main race is the combined time of runners who also completed the Everest marathon last year.
The leading contenders for the "double" are Sam Baker (Tokomaru), Simon Maister (Wellington) and David Brinson (Wellington) who finished third, fourth and fifth in the Everest marathon.
Maister was a member of the New Zealand hockey team that won a gold medal at the Montreal Olympics in 1976.
The oldest runner in the field is Te Anau's Ray Willet (72), who will be competing for the 20th time.
Bev Thorne (Te Anau) will be competing in the women's event for the 19th time.
