But the world certainly knows what she can manage when she is racing at "about 90%".
The 20-year-old Palmerston rider made a stunning debut in the women’s world motocross championship, winning both races in the opening event in Qatar.
She did not button off at the Netherlands event either, winning the first race and placing fourth in the second despite crashing when she was well in control of the race.
It seem nothing could stop the rookie if she could just stay on her bike — queue the errant photographer who had strayed too close to the edge of the track during the first race of the German round.
Duncan collided with said photojournalist and came crashing down.
So, too, did her world championship prospects.
Somehow she gritted her teeth and rode through the pain to finish the race in 12th place.But she had sustained a hand injury which required corrective surgery.
She was forced to miss the next two events while she recovered but returned to win the final two rounds. It was a bittersweet feeling.
"I went back and won the final two GPs and, in a way, it was really nice," Duncan said.
"But in another way it was like, ‘Jesus, this photographer really cost me the championship’.
"It still annoys me. And there are still days were I’m like, ‘Damn it’. But it is in the past now and I’m focused on the next season already. I’ve just got to try to do everything to make it happen next year."
While Duncan was able to slip into Qatar without much attention, she will not have the same luxury next season.
The other competitors know how capable she is of leaving them in her wake and will be desperate to find some extra speed.
But then Duncan, whose next assignment is the New Zealand MX2 series beginning next month, will be quicker as well.
"It is obviously still going to be tough because you are on the world stage and there is nothing that is going to be easy about that. But I’m going to know a little bit more before I head over.
"I’ll know how the schedule runs, how tough the sand is and already have good settings for the suspension and bike.
"I know what I’m going to now."
Duncan has a good team behind her who all play their part, but two contribute more than most.
Her coach, Josh Coppins, is there every race day to provide advice and help out, and mechanic Bjorn Stokmans makes sure her bike is running smoothly.
He is also on the stopwatch so Duncan knows where she is in relation to everyone else in the race.
One aspect of the campaign Duncan plans to do differently is that she will not travel back to New Zealand between events and will stay at her base in Belgium.
Spending more time in Europe will help her adjust to the different tracks and demands of racing in that part of the world.
While the conditions proved one of her biggest challenges, when you break down Duncan’s season, she was only beaten once when she managed to stay on her bike.
A fabulous effort, obviously. But it also raises the question of whether she had perhaps pushed too hard in some of the races.
"To be honest with you, I had only been racing at about 90%. I have not rode to my full potential in Europe."
That should make alarming reading for her rivals.
