The All Blacks looked set to ram home their 34-6 halftime advantage but their No20-ranked opponents stayed with the defending champions, although their under-powered scrum contributed to a stop-start second half which led to an underwhelming finish.
"It was frustrating, but we got an 80-minute hit-out into us and 29 out of our 31 players have played with no injuries," Hansen said.
"We scored nine tries which is a pretty good effort.
"It's very hard to play rugby when you have a stop-start game like that. We got a little frustrated but we got through that and it was a good learning curve for us. I'm really happy for Namibia, we had them in the changing sheds and they're a good bunch of guys. I thought they acquitted themselves tremendously."
Asked if his team had to have a mental strategy to combat teams and match officials slowing things down, Hansen said: "We've got to deal with it better than we did tonight anyway. It is difficult when every time you have a scrum... I think at one stage there we spent about four minutes [on a scrum] and that's not what the game wants. I don't know how to fix it. That's what happens sometimes when you get opposition who are struggling to stay up and we're struggling to stay up and the game doesn't need it."
Romain Poite's whistle dominated the second 40 minutes, along with TMO George Ayoub who wasted no opportunity to get involved. Asked about the TMO's interference, which is becoming a theme at this tournament, Hansen said it was important to get things right, but: "When you get a game like tonight the goodwill probably goes out the door - and you get frustrated. I'm talking about the fans rather than us as players and coaches."
As for the Namibians, who put pressure on the All Blacks lineout and scored a superb try through second five Johan Deysel, he said: "They committed themselves totally to the breakdown and to the tackle. They competed well at the lineout and they should be really proud of themselves. To achieve what they have done by just making the World Cup... and I don't mean that disrespectfully, I'm praising them for that. For half their team to be amateurs and be an event like this is an achievement in itself. I'm happy to acknowledge that they were worthy opponents."
Skipper Jacques Burger, an inspirational figure for his team, said he would have liked to have kept the score under 50 points, but his team would be better for getting their first game of this World Cup over with.
"Half of these boys are 8 to fivers [amateurs] and to play against the All Blacks on the world stage and face the haka was a special moment for us," he said.
"I'm glad the uncertainty is over. The boys realise it's just another XV human beings you're playing against. They're special and incredible rugby players but it's that uncertainty of the deep ocean, almost. You don't know what's under the water so you're afraid of it. We've learned a lot of lessons from that."
Namibia play Tonga in five days in the hope of breaking their World Cup duck, with the All Blacks facing Georgia in Cardiff in eight days.
