Derby manager Nigel Clough delivered a damning verdict on his team after they became the latest victims of Doncaster's climb up the Championship table.
Another goal from Billy Sharp, his sixth in as many games, and a late James Coppinger strike condemned Derby to a miserable afternoon at freezing Pride Park as they slumped to a 2-0 defeat.
Doncaster's fourth consecutive win ended Derby's four-game unbeaten run and Clough was clearly not happy at the way his team were beaten on a pitch dusted with frost.
"We have talked about a level of complacency recently that might creep in," he said. "You never know when it's going to come after the recent run we have been on but it did here.
"The first 45 minutes was very disappointing. I don't know if it's complacency, an air of arrogance or it might be we are not good enough. Perhaps it's a combination of all three.
"We've got into old habits and that's the reason Derby have not been out of the bottom half of the table in two and a half years. The two goals we have conceded were almost comical. We have been very solid recently but here we have given away two goals."
