Sheffield United's hope of automatic promotion virtually disappeared as George Burley's struggling side picked up a priceless point.
Blades boss Neil Warnock had demanded maximum points after Saturday's win over Bradford City to give his side any hope of catching Norwich and West Brom.
But a hotly-disputed penalty gave Derby a first division lifeline after Andy Gray had fired United into the lead The hosts went close in the opening minutes when, after a neat build-up in midfield, full-back Rob Kozluk crossed to the far post for Jack Lester to pull his header wide from six yards.
The breakthrough came in the 21st minute. Derby failed to clear and the ball fell to Gray who turned quickly to beat Lee Grant with a low shot.
The Rams hit back in the 25th minute from the penalty spot, Nick Montgomery appearing to make no contact as Leon Osman tumbled. Former Aston Villa midfielder Ian Taylor stepped up to coolly tuck away the spot-kick.
Kozluk cleared a Manel header off the line and Adam Bolder foiled defender Phil Jagielka in similar fashion minutes later before Manel broke clear with Paddy Kenny producing a vital save, deflecting the shot with his legs.
The United keeper brought off a spectacular stop minutes before the interval, clinging on to a long-range Marcus Tudgay header while Montgomery threw away a chance, pulling his shot from the edge of the area wide.
Kenny kept out Tudgay's 15-yard volley in the 61st minute, before United almost snatched the lead again, Lester weaving into the area before finishing with a right-foot strike that was spilled by Grant before being hacked to safety.