Watford head coach Gianfranco Zola admitted he had failed to do his homework after his team were thrashed 5-1 by Derby at Pride Park.
The Hornets were stung by three set pieces as Derby exploited awful defending to romp to their first victory of the season and Zola took the blame.
"I apologised to the players because I underestimated the value of this team at set plays," he said.
"I said to them 'it's my fault'. There are not many positives to say about this because the result is big and it's been a poor performance."
Zola accepted the sale of centre-half Martin Taylor to Sheffield Wednesday yesterday had not helped, but added: "The rest of the team must take responsibility and do better and that's everybody, including myself.
"I should have been more aware of the dangers of the opposition.
"We started okay but it was a poor reaction to the first goal, we just kind of stopped playing. They deserved to win but this is the Championship and if you give away cheap goals like we did for the first two then you are in trouble and that's what happened to us.
"As soon as we conceded, we stopped playing and that's not good enough. You have to be brave and play forward, not backwards."
Derby coach Andy Garner was delighted with the team display and the performance of striker Conor Sammon who scored his first goal for the club.
Garner said: "We are a little bit disappointed we conceded a goal but we are not going to say too much about that to the players after the effort and performance they've put in. Nothing takes away from the result and what the players have done today.
"We were disappointed at Wolves last week. You could see the players were disappointed not to get all three points after that performance and they carried that on in training this week and carried it on today.
"Conor was absolutely brilliant. I fancied him to score today and I said that to him in the warm-up and he thought he would score as well.
"He's still got a little bit more he needs to do work wise and fitness wise because of his lack of games but that will come. He works tremendously hard in training and he's only going to get better for Derby.
"His goal typified what we have seen from him since we started watching him playing up in Scotland, his determination to keep going and he thoroughly deserved his goal."
Watford's nightmare began in the 15th minute when Richard Keogh headed in a free-kick at the back post and the marking was non-existent when Jeff Hendrick rose to head the second from another set piece in the 36th minute.
Sammon then went past Carl Dickinson too easily to lob over Manuel Almunia two minutes before half-time and the contest was over when a Jamie Ward free-kick was pushed out by Almunia and went in off Will Hughes in the 51st minute.
More dreadful defending gave Ward a simple tap-in after 67 minutes and although Matej Vydra turned in a low cross in the 74th minute, it was not even a consolation.