Peter Taylor was unhappy with his team’s defending after conceding three times on Saturday.
Chesterfield scored twice in the second half to win the game 3-2.
Taylor side came back from 2-0 down to draw level, only to concede again.
The manager said: “The first goal was unlucky for us as it was a deflection. People were closing down and you can’t do anything about that.
“The second and third goals were disappointing for us.
“We could have dealt with them with voices and people making decisions. That is where it is a little frustrating.
“We didn’t deserve to be 1-0 down at half time, I thought we had a couple of good chances as well, but we were (behind) and that’s how it goes.
“I am disappointed because we got ourselves back in the game with some great character and we then let in another poor goal.
“The third goal is a really poor goal and you then think, ’that’s it, you’ve blown it’. In the last 10 minutes we certainly went direct and I felt we were going to get a goal.”
Chesterfield’s league form was poor before the game, but they made life difficult for the Gills, even though their 19-goal striker Eoin Doyle was left on the bench after picking up a knock.
“I was impressed with Chesterfield,” said the Gills boss.
“They really worked hard as a unit and made it very difficult for us. They broke out really well but I felt late in the game when we got the equaliser I felt we were looking better than them.
“Early doors, apart from their first goal, I thought we looked quite solid but then after that after giving away two really bad goals second half we were chasing the game.
“We had a fantastic opportunity with the last kick of the match (through Cody McDonald) and I thought the goalkeeper made a good save.
“The players are down but we know this is a tough league.
“The effort was really good in the end and we created enough things. It made for an exciting finish but unfortunately a disappointing one because we’ve lost 3-2 at home.”