The Chesterfield manager was left fuming after seeing Shrewsbury take all three points from Saturday's clash of play-off contenders.
"It was a poor performance," he said.
"I didn't think we got going. I made some changes to try and give us a bit of a start but that didn't happen.
"For some reason we just didn't get going until they got a man sent off and performance wise, it was probably our worst of the season."
The Cobblers meanwhile will be full of confidence after an excellent festive period and a win at Bournemouth that has reignited hopes of a place in the top seven at the end of the season.
The two sides met at Saltergate back in August when Donal McDermott's goal gave the home side all three points.