Derby manager Billy Davies felt some aspects of his side's performance against Birmingham were 'horrendous' as they suffered a 2-1 defeat.
Cameron Jerome put the Blues in front after just 32 seconds and although the Rams levelled through Matt Oakley, another well-taken Jerome strike gave the Blues the win.
'It is individual mistakes that have cost us. We have to be more disciplined individually,' Davies said. 'It is all about defenders defending and over the last few weeks we have given players too much space and time.
'There were patches in the game where they gave us some good stuff, but it is the little things which are costing us dear.
'There was some horrendous marking and some horrendous defending and concentration. We talked about it before the game, we talked about learning from last week - apart from splitting people's heads open and dropping a note inside, the words could not be any clearer.
'We proved there are one or two at this moment letting us down. It is disappointing because in the second half I felt we had them on the ropes.'