Wayne Rooney insisted that Derby's 4-0 win at Birmingham had been coming as they produced their biggest victory of the season to climb out of the bottom three.

Having begun the night as the Sky Bet Championship's lowest scorers with only 10 in 20 matches, and having only scored two in a game once before, they did the damage with three goals in 10 first-half minutes.

Krystian Bielik and Colin Kazim-Richards both scored from in-swinging Graeme Shinnie corners, while the Scot added a penalty in between those goals.

Jason Knight added a fourth late in the second half, leaving Rooney to reflect on a very good night's work.

"That performance has been coming over the last few weeks," he said. "I'm delighted for the players and I'm starting to see a team that believe in themselves.

"They have been putting in good performances, the results have been getting better, and even though we lost against Preston, the performance was excellent.

"You can see the confidence growing in the team. They deserve that for the work they have put in over the last month."

Rooney's Rams were hungrier and sharper from the off and the former England captain admitted it was a deliberate ploy as they sensed weakness in the Birmingham ranks.

"With the energy we have in the team, I felt it was the perfect game to take it to Birmingham," he said.

"I wanted to see if they could live with our energy and our desire and I felt we could overrun Birmingham and that's what we did."

Derby began the night in the relegation zone but, after watching that, the interim Derby manager is confident that his side are looking upwards.

"I'm not worried," he said. "We've got a lot of quality and hopefully with a few players coming in January, we can iron out some of the cracks and take us to that next level."

While Rooney was looking upwards, it was a bleak night for Birmingham boss Aitor Karanka. His side have not won any of their last five and are without a home win since October 28.

And the Spaniard blamed bad individual errors for their awful display.

"I'm not happy with the situation," he said. "It's difficult to understand.

"It's like going to the cinema and watching the same film. One mistake, one goal. Two mistakes, two goals. Three mistakes, three goals.

"It's difficult to accept but it is something we are suffering. And it's hard to understand when one game you are perfect and the next game you make the same mistakes as a couple of games before.

"That is my frustration."

Karanka is only a few months into the job at St Andrew's, but it looks like it could be another season of survival for Blues.

He added: "I apologise to the fans. But they must keep belief in the team. Three days ago we did well, so why not the same?

"I expected ups and downs this season, but not these same individual mistakes every single game."