DERBY 3 (Sammon 16, Buxton 66, Davies 90+4), LEEDS 1 (Green 45)
Derby: Legzdins, Brayford, Buxton (O'Brien 79), Keogh, O'Connor, Coutts, Hendrick, Jacobs, Hughes (Freeman 90), Robinson (Davies 82), Sammon. Subs: Fielding, Doyle, Tyson, Bennett
Leeds: Kenny, Byram, Tate, Lees, Peltier, Tonge, Green, Norris(White 79), Hall (Varney 68), Becchio, McCormack (Diouf 74). Subs: Ashdown, Pearce, Brown, Gray.
Referee: S Mathieson
United manager Neil Warnock made just one change to his starting line-up for the trip to Derby, Ryan Hall coming in for the injured Jerome Thomas as his side went in search of a fourth successive victory.
United had accounted for Crystal Palace, Leicester, and Huddersfield in the last three games while Derby had endured a less than successful run that had produced just one win in five.
The hosts did win a couple of early corners, though, Theo Robinson having a header deflected over after a Paddy Kenny clearance had crashed against one of his own defenders. United's first sight of goal came on 14 minutes when Ross McCormack floated a free-kick wide.
But, moments later the home side got their noses in front when Conor Sammon found space to latch onto a through ball and he slotted the ball past Paddy Kenny to make it 1-0.
The United goalkeeper also had to block from Robinson as the hosts enjoyed much of the early pressure. On another break forward, Tom Lees did well to deny Sammon.
There were a few feisty challenges in the first half and Jake Buxton could perhaps consider himself fortunate to escape with a yellow after one on Ryan Hall.
The opening period looked like belonging to the home side. Derby had dominated possession and United had been unable to find any real fluency. but the scores were levelled right on half-time.
Former Derby midfielder Paul Green, made captain for the day, was the man who capitalised on a knock-down in the box to apply the finishing touch after good work by Lee Peltier and Luciano Becchio.
The goal was the perfect boost for Leeds right on the stroke of half-time, and United came out of the traps flying at the start of the second period, winning a corner and applying some early pressure. The hosts had to make one desperate headed clearance and Derby were firmly on the back foot as United attacked the end housing 4,000 strong away following.
The game had certainly opened up by the hour mark and the hosts were again looking to thread the ball through to Sammon to capitalise on his pace.
Will Hughes also had a shot blocked from distance before Kenny had to react well to beat away an effort after he cut in from the right.
Lees also made a decisive header in the six-yard box after a corner, but Derby scored from the resultant set-piece when Jake Buxton capitalised to drill the ball home.
Now, it was United's turn to press for an equaliser for the second time, and David Norris was only denied by an instinctive save from Adam Legzdins after the ball fell to him on the edge of the box.
Green was instrumental in driving Leeds forward, and with 15 minutes left on the clock, Warnock brought on El-Hadji Diouf to join fellow sub Luke Varney as Leeds attempted to find a way back once again.
And when Diouf supplie a good cross from the right, Lees could only watch as his header came back off the inside of the post before being hacked to safety. Diouf also sent a shot fizzing wide of the upright with just over six minutes remaining.
Aidy White was also introduced to add a late injection of pace and his first involvement was to send in a cross which Diouf met first time, but shot just wide.
In the final minute, when United came forward, Green felt he had claims for a penalty when he went down in the box, but referee Scott Mathieson waved play on.
Four minutes were added on at the end of 90, and in the final of those minutes Derby wrapped up the victory when Ben Davies steered the ball home.