A fourth round 1-0 defeat by Blue Square Premier Luton Town at Carrow Road meant the Canaries became the first top-flight opposition to be beaten by a club from outside the Football League in 24 years.
And after watching Scott Rendell's 80th minute goal eliminate Norwich, Hughton, whose side have taken just one point in their last six league games, knew they had paid the price.
"They came with a game plan and we found it very difficult to break them down," Hughton said of Luton, who are managed by his former Brentford team-mate and friend, Paul Buckle.
"The good chances that we did have, we were not able to put them away. If we get one of them, the game changes a little bit.
"But even in the second half, there was a period where we pushed and pushed and they caught us on a classic counter-attack.
"It was a poor goal to concede."