On a day of frequent showers, the angry home supporters were in no doubt which was the biggest shower of the lot – their Nottingham Forest team. A huge dark cloud hung over the City Ground at the end, ready to unload another torrent on to the masses, and it could get darker for Forest before they start to see some light.

A third successive defeat was bad enough for Steve McClaren, the embattled Forest manager, but that it came against Derby County, their bitter East Midlands rivals, made it all the more galling. That Derby played for virtually the entire match with ten men, after the sending-off of the goalkeeper, Frank Fielding, only proved to exacerbate McClaren's discomfort.

That of the fans, too. A section of them unfurled a banner proclaiming "Arthur Out" – a reference to Mark Arthur, the Forest chief executive – and chanted "Sack the board". The three-month tenure of McClaren, the former England manager and former Derby player and coach, appears increasingly vulnerable.

And, once again, he hinted that a lack of transfer funds was holding back the reshaping of his Forest squad. "I knew this would be a tough job," McClaren said. "We really let the fans down and we have to do a lot of work with our shape, the personnel, everything. But we need help on and off the field."

It was not long ago that Forest were nigh on unbeatable at the City Ground. Until March, that is, when their 36-match undefeated home league record ground to a halt in their 1-0 loss against Hull City. Forest have been no better than patchy on their own turf since but received the welcome bonus of Derby being reduced to ten men after only 66 seconds, when Fielding, the goalkeeper, bundled over Ishmael Miller as he shaped to shoot.

"I haven't seen it again but I thought it was more of a collision than anything else," Nigel Clough, the Derby manager and son of the former Forest legend, Brian, said. "It was just one of those things."

Adam Legzdins replaced Fielding from the bench, with Tomasz Cywka sacrificed, but Andy Reid thundered the penalty past him.

Eleven v ten should have signalled better fortunes for Forest, but they quickly grew frustrated as Derby battled resiliently at the back and in midfield. In fact, Forest imploded in bizarre fashion in the 29th minute to allow Derby to draw level.

Chris Cohen, the Forest left-back, fell to the floor awkwardly in the Derby half, injuring a knee, and was attended to by Miller, effectively reducing the home side to nine men. The referee, Scott Mathieson, waved play on and Jamie Ward was allowed to weave his way through to score from the tightest of angles. "It was a brilliant individual effort," Clough enthused.

Yet should not Forest have done more than plead with the Derby players to kick the ball out? Like tackle Ward, for a start.

"I wouldn't have stopped, I would have played on," McClaren said. "It's up to the referee." Matt Derbyshire expended more energy in lambasting Ward and Mathieson after the equaliser than he had done in trying to prevent it. "It's not our job to stop play," Clough observed. "We play to the whistle."

Still, Forest continued to fail to make their numerical advantage count. Not even after a series of frantic efforts early in the second half, with Reid, twice, and £1.2m striker Miller both unable to find the target. Jeff Hendrick should have punished them when he missed a sitter of a header from a Ben Davies cross, but the Derby midfielder made amends when rifling in a low shot past Lee Camp. And the skies – and omens – just got darker for Forest.