Gareth Ainsworth admitted sloppiness cost his Wycombe side after losing 4-3 to Norwich in a Carabao Cup third-round thriller at Adams Park.
Jordan Rhodes' 10th career hat-trick, including two in the first 15 minutes, alongside Tom Trybull's first-half effort looked to have sent the League One side out with 40 minutes still to play.
But Sam Saunders' penalty and Adebayo Akinfenwa's bundled goal set up a tense finish after Paris Cowan-Hall had got Wanderers back into it in the first half.
"We let a couple of sloppy goals in before half time and that's ultimately cost us," said Ainsworth.
"You can't go giving yourself mountains to climb like that. There were some good players out there and you could see the difference in class at some stages.
"But I thought heart-wise and endeavour we matched them, and we almost got that equaliser at the end.
"I'm always proud of my boys; they never give me anything less than what they've got and it's just that little bit of quality and maybe a bit of questionable defending in the last minutes of the first half were costly things.
"We know Norwich like to take chances going forward that they do leave themselves open at the back, and maybe the goals didn't come the way I thought they would, but we did put a lot of pressure on them in the second half."
Norwich are now into the fourth round having already knocked out Premier League side Cardiff, leaving manager Daniel Farke daring to dream big.
"Our offensive play is so dangerous, we scored four times and the referee denied us a clear goal and that is how it is sometimes," he said.
"I'm a deep believer in cup competitions and I'm a big fan of this cup. Of course, it's not realistic that a Championship side is able to win the Carabao Cup but sometimes in football you try to reach some extra things and not just realistic targets.
"We are in the fourth round and happy with this. It's well deserved after some really good performances including away at Cardiff who are in the Premier League and let's see how far we can go.
"You have to defend long balls with Akinfenwa when he comes into the side, sometimes they score from this situation. The last few minutes were spicy but it is how it is and we're through to the next round."