Gary Mills bemoaned the fact York failed to produce a second half display to match their first 45 minutes, going down 3-0 to Chesterfield.
The visitors had the better of a goalless first half but were hit by a goal in the opening minute of the second period from full-back Drew Talbot.
Chesterfield made the game safe with two further goals inside two minutes, substitute Danny Whitaker scoring within a minute of entering the action and Tendayi Darikwa netting in the 77th minute.
A rueful Mills said: "It's a 90 minute game and we've got to play the second half like we played the first. We were on the front foot, our shape and ball retention were very good and we made it difficult for them.
"We had two or three half chances in that period, they never had a chance and I thought we were excellent. In the second half we weren't as good.
"You can't concede as early as that, right from the throw in that led to their first goal I thought we were too deep, whereas in the first half we were in their faces and on the front foot.
"Forty-five minutes is not enough to get a result in this league. We've got to keep our shape, keep our standards up for the whole game and unfortunately that wasn't the case."
He highlighted a key moment just three minutes after Chesterfield took the lead, when York striker Jason Walker appeared to be fouled inside the penalty area by centre half Liam Cooper only for referee Chris Sarginson to rule no foul.
"It looked a penalty to me, Jason's saying it was, everyone appealed for it and I don't know why the referee looked over at the linesman because he was looking at it and had a clear view of it."