Crawley Town boss John Gregory said he was "embarrassed" by his team's performance after Rochdale had thrashed them 4-0.
Matty Done put Dale ahead with a tremendous first-half strike before a double by Peter Vincenti and a header by substitute Calvin Andrew secured the visitors their second league win of the season.
Crawley have lost their last four league games and former Aston Villa boss Gregory believes poor defending cost his men.
He said: "Overall it was a very poor performance. I don't think I've ever been involved in a game where I've lost at home by that score.
"The fans were singing that they were embarrassed. I am more embarrassed than they are.
"For the first three matches of the season we were watertight - here our defending was very open.
"They had five opportunities at our goal and three of them went in. I wish we had the same kind of ratio at the other end."
Gregory said he was concerned his players have found the net just three times in their opening six matches and described the defeat as the "worst performance" since he joined the Reds in December last year.
He added: "We didn't particularly look like scoring at all, which is a worrying trend that has surfaced in the last couple of games.
"We scored two against slightly inferior opposition (Cambridge) in the Johnstone's Paint Trophy in midweek, so I didn't get too carried away with that.
"But it's hard to recognise too many of my boys in this.
"We can't afford to have results like that. It'll be a long week now. It's by far the worst performance we've had since I've been here."
Rochdale manager Keith Hill said his side's victory was reward for their efforts following a challenging start to the season on their return to Sky Bet League One.
Dale's only previous league victory came at Crewe, but Hill believes his side are making progress and offer a dangerous threat in attack.
"This is reward for a difficult start to the season," he said.
"We didn't come here with any real expectations. Our plan evolved and it transpired in us winning 4-0.
"It looks comfortable on paper - but in reality, like every game in League One, it was far from comfortable.
"We are making progress and making big strides though.
"We have goals all over the pitch. Matty Done, Peter Vincenti, Calvin Andrew are all a threat and right now I'm happy."
Hill insists that it is no coincidence his men have won their two previous matches following the return of defender Jack O'Connell to the club.
O'Connell made 45 appearances for Dale last season and re-signed on a four-month loan deal from Blackburn on transfer deadline day.
Hill added: "It is absolutely no coincidence that we've had Jack in the side for the last two matches and won.
"Jack was the one player who, if I could have sold my house and bought him in the summer, I would have done so.
"But I can't leave my wife and children homeless, which is why it has taken so long to get him.
"You could see what a good defensive unit we were with him in the side though - the whole team pressed from the front."