Carl Baker had put the Sky Blues ahead, but two Leon Clarke goals saw the Iron leave the Ricoh Arena with a well-deserved three points
He said: "On the back of Tuesday night's win and the games we have played recently I expected us to come in and have an assured confident performance. We didn't get it.
"The penalty was harsh. But I also think we have to be better in terms of defending it because when the player on the ball has time you have to give ground and go with your runners.
"The naivety of the defenders we have, at times, costs us goals and costs us points. If we had taken the chances that we created then we would have won but we didn't and their goalkeeper made two, maybe three, outstanding saves towards the end of the game."