Derby pointed an accusing finger at referee Mike Jones after a controversial late penalty gave Walsall victory in the relegation battle at Pride Park.
The Cheshire official awarded the visitors a spot kick despite his linesman flagging for a free kick to the home side.
Derby manager George Burley said: "The linesman put his flag up straight away for a free kick for us and the ref has awarded a penalty.
"The ref has won the game for Walsall today." Walsall manager Colin Lee had some sympathy for Derby and admitted: "I would be disappointed if I was in their camp.
"I must admit that is hard to swallow when you are down at the bottom." Derby were incensed when Mr Jones gave the penalty in the 86th minute and then sent off Michael Johnson for pulling down Lee Bradbury, who had two loan spells at Pride Park this season.
Bradbury took the spot kick himself but Derby's feeling of injustice did not end there.
They also felt Mr Jones blundered by failing to play advantage when Spanish striker Manuel was through on goal in the 61st minute and they also questioned the offside decision which denied the Spaniard a first-half header.
Those decisions could prove so costly to Derby while Walsall are now close to safety after this precious victory. The game itself was littered with errors and few chances to either side although Derby dominated throughout.
But Walsall defended stoutly and goalkeeper James Walker pulled off a marvellous save in the 56th minute to keep out a Leon Osman volley from ten yards.
The match appeared to be drifting towards stalemate when Bradbury and Johnson tussled for a long ball with four minutes left.
Bradbury seemed to pull Johnson before he was dragged over but the ref produced a red card before he went to consult with his linesman.
Bradbury beat Lee Grant although the keeper got a hand to the spot kick as he dived to his right and the drama continued into stoppage time.
Former Walsall striker Junior, who marked his return from a serious knee injury by coming on in the last 11 minutes, had a shot cleared off the line by Simon Osborn.