The top seed will have to be on top form to bag another win tomorrow.
Ussher (42), of Nelson, who finished fourth last year, knows the course well and has strength in all disciplines so will be difficult to beat.
Last year's winner, Robyn Owen, is not returning.
Ussher has had a short build-up, taking it easier after an intensive period of racing in China in September and October and competing in the Pioneer six-day mountain bike stage race in November.
Simone Maier is arguably the strongest female competitor in New Zealand in all disciplines. She has never won the race - finishing second and third - so will be very hungry for it this year.
Maier, of Wanaka, has had her shortest build-up for the event but said she was feeling good about it.
"I've had no injuries or sickness so I feel good," she said.
"I have trained well for it and I feel I'm ready to race hard and enjoy the scenery along the way. I want to race my own race and have fun and then the result will take care of itself.
"Every time I race I'm aiming to win. It is an amazing course and I just like to see what I can do on it, going hard and feeling great, but you don't get many of those days as there are so many elements that can happen."
How Swedish adventure racing champion Marika Wagner does at her first attempt will be interesting.
Wagner said she was just looking to compete and perform well, and it had been a big goal to take part.
Whakatane's Corrinne O'Donnell is another contender after making a name for herself in adventure racing over the past year.
Other contenders include Australians Bern Dornom and Leela Hancox while Claire Bell, Isla Smith, Fiona Dowling and Georgia Whitla are all potentially podium finishers.
