Louie Sibley scored a dramatic stoppage time winner to give Derby a 1-0 victory over fellow relegation candidates Peterborough.
The substitute broke Peterborough’s hearts with a low cross-shot when it seemed the game would end in stalemate.
Both sides had been reduced to 10 men with Peterborough’s Hayden Coulson sent off for two yellow cards in the first half before Tom Lawrence was red carded for a late tackle early in the second.
Chances were few and far between with Peterborough failing to register a shot on target as their goalless run was extended to five matches while Derby go above the visitors.
Derby brought in 20-year-old central defender Eiran Cashin for his first start in a game that meant so much for both clubs.
Roared on by another 30,000 crowd, Derby started strongly with Lawrence forcing Steven Benda to turn behind a shot in the 11th minute.
Peterborough weathered the early pressure and after a decent spell of possession, almost carved out an opening in the 20th minute when Joe Ward’s deflected cross was just cut out by Ryan Allsop.
Derby responded with a quick break in the 29th minute that ended with Festy Ebosele firing in a low shot from just inside the box that was blocked by a blue shirt.
There was a major setback for Peterborough in the 35th minute when Coulson was sent off for a second yellow card in four minutes when he tripped Ebosele out on the left.
The free-kick was only half-cleared and Max Bird’s shot from 20 yards was brilliantly tipped over by Benda.
Derby’s advantage vanished two minutes into the second half when Lawrence was shown a straight red card for a late lunge that left Nathan Thompson writhing on the turf.
It was a reckless challenge by the Derby captain but fortunately Thompson was able to continue after lengthy treatment.
Derby won a free-kick in a dangerous position just outside the box in a central area but with Lawrence in the dressing room, Bird failed to clear the wall and the rebound went well wide.
The deadlock should have been broken in the 63rd minute when Ebosele’s low cross reached Craig Forsyth at the back post but he skied his effort over.
Derby almost went ahead in the 74th minute when a Jason Knight cross came off Luke Plange and hit the foot off a post but Benda just stopped the ball going over the line.
But Sibley produced a moment of quality in added time when he beat Benda with a low drive that flashed just inside the far post to keep Derby’s hopes of staying up alive.
