Spireites manager Danny Wilson bemoaned his side's defensive performance after the 3-1 Proact loss to Millwall on Saturday.
Millwall scored their three goals before the break through Shane Ferguson and a Steve Morsion double and were unable to pull off a recovery despite Sam Hird's second-half header.
"The manner in which we conceded the goals was there to be seen, they were very very poor," said Wilson of the first half. "Defensively we were at sixes and sevens at times, when they were putting ball in behind us we looked like we were struggling to deal with anything.
"Sometimes you've got to be honest and brutal in your assessment: we couldn't handle Morison at all, he bullied us and that's got his team a good win.
"I can sit here and dress it up and say it wasn't that bad but the defending was bad and we've got to do better than that."
A couple of bright spots came from the bench with Reece Mitchell and Kristian Dennis showing promise when introduced. Wilson was pleased with the showings, especially from the former Chelsea man.
He said: "They both had an impact, particularly from Reece's point of view he's taken a little bit of time to settle into league football, which he's never played before.
"He's used to under 21 football and it's a bit tippy-tappy, this today was a proper man's game and against Millwall you've got to come in and man up.
"I thought he did well, and he was given a few testers. He's done well, let's hope he can get to the pace of things as quickly as we expect him to."