Cobblers boss Rob Page was left to rue individual errors as he reflected on Saturday’s loss against Millwall.
“I’m very disappointed with the afternoon,” he said.
“We started okay but we then fell into their hands a little bit and we’ve conceded three very soft goals.
“Individual mistakes are costing us and we need to eradicate those errors. We will address it and we will put it right.
“The sending off changed the course of the game, Jak McCourt’s young and he will make mistakes but he needs to learn from it. He’s been excellent for us but today is a harsh lesson for him.
“If you want a game to go and put things right in it’s a local derby and we need to put today to bed, learn from it and move on quickly to Tuesday.”