"He's played a lot of games for the All Blacks and, if this happens to be the end of his tournament, it would be a sad way to finish because he's been a great All Black and probably deserves to go out better than that," Hansen said after the Tonga game.
Wyatt Crockett replaced Woodcock in the 43rd minute, with Woodcock's body language suggesting he feared the worst.
The injury was the only negative of a performance which, especially in the second half, was impressive from the defending champions.
They finally found their groove on attack, with wing Nehe Milner-Skudder all but securing the No14 jersey next weekend with a mature, two-try display.
It was also a positive display from first-five Dan Carter, who had an excellent all-round match.
"He carried well," assistant coach Ian Foster said. "I thought his defence was really good. And his reading of some situations under a bit of pressure in the early part of the game, I thought he settled down and read it really well. Obviously his re-starts and goalkicking were excellent. He certainly went up a step."
The reserves, again, proved a difference against a tiring Tonga, who played Argentina only five days ago. Sonny Bill Williams was brutal on defence and picked up a try with an inside pass from Aaron Smith.
Beauden Barrett was also in good touch, laying on a try for Milner-Skudder with a kick through the defence soon after his arrival. Hansen said the final 30 minutes would set up the All Blacks nicely for their first knockout match.
"It doesn't matter who you are, confidence is a massive thing. From that point of view, it was good. What really pleased me was that the guys coming off the bench gave us a lift and that's their role.
"Next weekend is the start of finals football. The big boys get to stay and the guys who don't perform go home. We have to be ready for whatever comes at us."
The Tongans provided a physical test in the first half. They carried well and retained the ball extremely well. In the final minutes of the first half, they went close to scoring a try in the absence of All Blacks skipper Kieran Read, sinbinned for pulling down a maul.
"I really put our side under pressure, didn't I," Read said. "The guys responded really well.
"It's something we can be really proud of, that defence. We're really good at backing ourselves, not giving away a soft penalty or lacking that discipline. It's a step up and we're looking forward to a bigger challenge next weekend."