Justin Edinburgh felt his side were their own worst enemies on Tuesday night.
Defensive mistakes proved costly as they were soundly beaten by Chesterfield.
“They didn’t have to work hard for the goals,” said Gills boss Edinburgh, whose side were 2-0 down after 12 minutes.
“We spoke about how we were going to set out and what we were going to do, what were going to achieve, and within 10 minutes all of those things were undone.
“It wasn’t through Chesterfield’s good play, it was naivety, our slackness going against what we have been good at and it was extremely frustrating.
“It’s disappointing and for large parts of the game we were second best but we gave ourselves a mountain to climb being 2-0 down within 12 minutes. That was uncharacteristic.
“Once you are chasing the game like that you leave yourself open to be picked off. It is a very disappointing night.”
It was a second away game in quick succession for the Gills but Edinburgh wasn’t using that as a reason for their undoing.
He said: “There is a list of excuses but we prepared properly, we did everything correct.
”We know it’s tough but other teams have had to do it. It was nothing to do with that, it was that we were very naive in the first two goals in our play after just a few minutes on the clock.
"We were trying to play it out from the back, we spoke about having a fast start and putting them on the back foot but we did the opposite.
“It is difficult when you are 2-0 down, we huffed and puffed and we had a little period in the first half where we got ourselves in the game and apart from that Chesterfield have dominated and deserved to win the game.”