Ragot was third at last year's world championships in Italy and displayed top form when winning the first two races of the North Island series this month.
Ragot has beaten Hagen in World Cup and world championships events in the past, but Hagen has the advantage of knowing the Signal Hill Course.
"I'm hoping to beat her on Saturday," Hagen said. "But anything can happen in downhill racing."
Hagen (21), a second-year physical education student at the Univer-sity of Otago and a personal trainer, won the world junior title in 2004 and the Oceania title in Nelson last year.
Ragot is one of three overseas internationals competing on the Signal Hill course. The others are Scottish speedsters Ben Cathro and Joe Barnes.
Cathro won the first round of the North Island Cup on January 4.
They will be challenged by New Zealand downhill specialists Justin Leov (Christchurch) and Sam Blenkinsop (Wanganui).
Leov is one of the most experienced New Zealanders and has been on the podium twice in World Cup events.
Blenkinsop achieved a first for New Zealand male downhill riders last year when he won a World Cup event in Europe. He is ranked seventh in the world.
A large field of 150 mountain bikers is competing in the first of the three-event South Island series.
Rounds two and three will be held next month at Coronet Peak and Blenheim.
The 2km race is full of steep drops, jumps and rock gardens that will test riders' skills and nerve.
Other local riders expected to do well are Tim Mackersy and Eddie Masters in the professional field, promising junior Leighton Kirk, and Ant Jackson in the senior men's field.
One national mountain biking star missing this weekend is Dunedin's Sheryl MacLeod, who broke her neck on a training ride earlier this month.
The New Zealand downhill series consists of six races, three in the North Island and three in the South Island.
The overall winner becomes the national champion and automatically qualifies to compete at the world championships in Canberra in September.
The New Zealand championships will be held in Nelson in March. Training will be held on the Signal Hill course tomorrow from 10am.
Qualifying and racing are on Saturday from 10am. The finals will start around 2pm.
