The former Highlanders fullback picked up two tries in beating the French, including a try right after halftime, which extinguished any hopes of a French comeback.
"I just read the situation. I saw a couple of forwards there and thought I'd have a crack. You don't even think about it, really," Dagg said.
"I just go with the flow. Instinct takes over and I just went with it."
Dagg, now clearly ranked ahead of 98-cap fullback Mils Muliaina, had a splendid game at the back, making well-timed entries into the backline, and also kicking solidly.
"I'm pretty happy. I've got to thank the forwards. They gave us the ball and made it easy for us. Ma'a Nonu ran havoc and set it up for us guys to finish.
"To win is obviously good for confidence but we can't get too far ahead of ourselves really. This is a big tournament and to win this you've got to beat the best. We've just got to keep building and look forward to Canada."
Dagg was one of stars of the show, but not many of the men in black could be unhappy with their games, as the All Blacks sent out a warning to the other contenders at the World Cup.
All Black assistant coach Wayne Smith was happy with the performance and said there were patches where the backline excelled and followed the plan to attack at the right time.
"I think the timing of the pass was really good, especially the way we could put people into space. We didn't allow them to drift. The calling of the moves was really good," Smith said.
"We had a game plan and where we wanted to attack. Some of them worked pretty well and some of them didn't work that well. But we are building and hopefully getting better each week.
"We are probably are where we want to be at the moment... but maybe seven out of 10 to where we can be ... but we had some poor patches on defence and on attack. Overall you had to be happy."
Smith said there were a group of players who just loved to play, and Dagg was one of those.
"You can see it in their eyes. Game day is the best day of the week for him [Dagg]. They just love it. They just want to play, and get out there. He does not seem to feel the pressure and just wants to play.
"The key to us is we have to keep moving. Sometimes you have to take the eye off your opposition and worry about us. And that is what we have to do. We have got Canada coming up and we need to think about them but also look at us."
The home side should go into the match against the Canucks brimming with confidence, after a performance that made captain Richie McCaw's 100th cap extra special.
The All Blacks soaked up some early pressure from the French and then made the most of a Nonu break for Otago loose forward Adam Thomson to score after 10 minutes.
Winger Cory Jane then ran on to a delightful ball from Piri Weepu to get in behind the French defence and run away to score.
By the 20-minute mark, the side in black was home and hosed, with Dagg scoring his first after Dan Carter broke the French line.
The French had more attacking options in the second half and scored a couple of tries but the game was over by then.
Sonny Bill Williams, on for Jane, scored the final try of the match with less than five minutes left.
Although it would be hard to single out one All Black, Dagg was impressive, Nonu is playing as well as he has in the black jersey, and Carter steered the ship well.
Up front, McCaw was immense, while the front row was dominant at scrum time.