Mark Robins says his Sky Blues players must respond on Saturday after City were beaten 2-4 by Lincoln City at the Ricoh.
The Sky Blues were behind after just 55 seconds in a game that saw Robins' side draw level twice during the first half.
"I am so disappointed," said Robins.
"I can accept the first goal because he has hit it out of the blue, but the other goals are poor and easily stoppable.
"When you look on the face of it we have scored two really good goals and they have scored goals where they have lumped it forward and we have not dealt with it well enough. Even then the second ball we do not win. It is the second phase that we need to deal with.
"You expect your defenders to defend and we haven't had it. Our defenders have been really good this season but I keep saying the same thing every time. Whenever we get a chance to move forward we turn it down. You could write the script. They do not take advantage when it is there.
"If we are not willing to go and put out heads on things then we do not deserve to win a game."
Despite the result, the Sky Blues remain in the play-off places.
"We can still do this. We need four points. This game has just been annoying.
"The players have to be more aggressive. The supporters do not want to see this. I am really disappointed and really angry. I think our players have got to show that they want this. This club has been starved of success. The amount of points we have now are the most we have ever achieved in a season.
He added: "We have never been in a play-offs before and we need to change that. I want a response this weekend."