MILLWALL boss Neil Harris said referee John Brooks' decision to send off Ben Thompson was a "disgrace" after the Lions lost at home for the first time in the league in eight months.
Millwall fell behind to Rochdale when Callum Camps fired home Joe Thompson's cross in the ninth minute.
Aiden O'Brien equalised for Millwall two minutes later before Lee Gregory, making his first start in seven games, fired the Lions ahead from the spot in the 18th minute.
Millwall looked comfortable until Calvin Andrew headed Rochdale level in the second half, before Thompson received a second yellow card after Brooks felt he had fouled Matthew Lund.
And in added time Ian Henderson scored from the penalty spot after Jimmy Abdou had fouled substitute Steven Davies.
Harris was unhappy with Thompson's dismissal, but wasn't using it as an excuse for Millwall's defeat.
He said: "I've no real complaints with the first one, the second one is a disgrace, it's never a yellow card.
"I spoke to the referee, he was good enough to give me his time. He has got it wrong. He thought Ben made an honest challenge for the ball but has defended a counter attack to lead to a goal-scoring opportunity.
"Ben's watched the ball all the way and it's debatable who got first contact on it, Ben or their player. The ball then falls to Mahlon Romeo's feet, so there's no danger. It certainly didn't help us in our quest to win the game.
"I don't think the red card changed the game, but it certainly affected the game.
"I think the inability to be able to defend our 18-yard box has cost us. Yes we had chances to go further ahead and we should have scored again and put the game to bed at 2-1. But we didn't.
"We still scored two goals, but we've got to get back to a clean-sheet mentality, stop the opposition from sensing danger and ultimately keep the ball out of our net."
Harris said he had no problems with the award of Rochdale's penalty when Davies tumbled in the box in injury time, and he admitted it was also the correct decision to flag Fred Onyedinma offside after the substitute had finished Steve Morison's cross to the net in the 88th minute.
"No complaints with the penalty, it's a penalty," Harris admitted. "The first two goals were poor, naïve defending, naïve defending by young players.
"Defending set-pieces is a big part of the game, you have to do it. Rochdale have size and presence and attack the ball well.
"It's fine lines, football. Fred's a quarter of a yard offside – and he is offside – a quarter of a yard from us winning the game. Two minutes later they get a penalty and win the game."
Image source: ©Charlie Compitus