The performance was an encouraging one, but Hansen wants to keep everyone on their toes as the potentially crucial clash with the Kiwis draws closer.
Hansen said: 'Every time you play, you are playing for your spot.'
'It doesn't matter who you are playing against. When you are in the red jersey, you have got to perform if you want to play in it again.'
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Iestyn Harris, who shone in the Canada match, is rested, allowing former British and Irish Lion Mark Taylor a chance on the World stage.
Hansen's four changes up-front mean starts for prop Iestyn Thomas, hooker Mefin Davies, lock Robert Sidoli and back-row forward Alix Popham.
Tonga will present a different challenge to that of Canada. Hansen expects the South Sea island side to be going all-out for the points after their 36-12 defeat to Italy in the opening pool match.
'Against us, I think Tonga will throw the ball around and throw everything at us. It is win at all costs for them, and if they don't get any points, then their tournament is all over,' he said.