Derby County manager Steve McClaren has admitted that he is concerned about his side's defensive form following their 3-2 win over Sheffield Wednesday.
The Rams were twice forced to come from behind before Darren Bent secured them all the points from the penalty spot in a thrilling Championship match at Hillsborough.
However, McClaren had conceded that his side will need to improve at the back if they are to remain top of the table.
"We've had spells of six or seven clean sheets but in the last four we've conceded nine goals," he told reporters.
"We can't continue with that and I thought today we are going through a spell where we make a mistake or give a free-kick away and it's a goal. But we have to eradicate mistakes otherwise conceding nine goals in the next four games will get us nowhere.
"We said to the players at half-time that this could be a very big three points if we comeback and I think in the end we wore Wednesday down with constant pressure and the tempo of our football."
Derby, who are now unbeaten in six games, are back in action against Charlton Athletic on Tuesday evening.
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