The Whites were soundly beaten by their League Two opponents and McAllister was disappointed by what he saw.
"Defensively we were poor, we can't hide from that. People have to stand up and be counted. In our box people didn't get their heads to the ball and protect our goalkeeper," he said.
"There's a lot of nice things being said that we like to pass the ball and our forward play has been excellent, but we've only kept a couple of clean sheets and we have to step up.
"I think they had five attempts on goal and scored from four. They scored with their other attempt, but that was disallowed."
The Millers began the season on -17 points, but after a storming start to the season have given themselves every chance of avoiding relegation to the Blue Square Premier.
They have already knocked three Championship clubs out of the Carling Cup this season and followed those feats with a convincing win over their Yorkshire rivals.
"It was a great feeling to win, but what I was particularly pleased with was the manner that we did it in," said their manager Mark Robins.
"We put in a really good disciplined performance, which included some quality football and we deserved to go through."