Blues led the Rams 2-0 with an hour of the game gone and were seemingly assured of a comfortable home win.
However, lacklustre defending allowed the visitors back into the game and Nigel Clough's side left St Andrews with a share-of-the-spoils.
"It was very frustrating. At 2-0 up the fact you're playing at home, you fully expect to go on and win," the Blues boss said after the match.
"What we have done perhaps in the last couple of games is conceded uncharacteristic goals, by our standards of where we have been.
"That happens. It's very difficult to go through a full season without having some of the lows to go with the numerous ups we have had.
"Probably at the moment, with the Forest game last week, and the Derby result it's a little bit of a low for us.
"We have to learn from it and look to pick it up again for the next league game."