Villas-Boas said that credit must go to the visitors for the way they approached the game, but conceded that his team were below par.
"The first half we were not so sharp, like last week," the Portuguese told Sky Sports News. "Second half we improved a lot and had more of the ball.
"In the end we suffered again from a set play. It's obviously disappointing but we will look to repay our fans with a win they deserve.
"[Norwich] were sharp and very objective, so you have to give credit to them. We always looked on the back foot in the beginning, but we improved in the second half."
Spurs travel to the Madejski Stadium to face Reading in their next Premier League game.