Steve McClaren praised Derby's impressive work-rate after they set a new club record of seven consecutive home clean sheets with a 1-0 win over Birmingham.
Darren Bent hit the winner from the penalty spot in the 64th minute after Michael Morrison tugged Richard Keogh following a corner.
The goal secured Derby their eighth win in nine matches and was just reward for a dominant display. The visitors were unable to register a single shot on target.
Bent had an effort ruled out for offside after 35 minutes and nearly broke the deadlock 10 minutes after the break after latching on to a loose back pass.
Johnny Russell wasted two good chances to make the game safe in the closing stages.
McClaren said: "The clean sheet is a team effort. You saw the work Russell and (Tom) Ince do.
"We are disciplined and the back four get good protection from the front.
"When they get through the back four or the goalkeeper deals with it. It's the platform for our performances."