FRANK LAMPARD saw off old boss Jose Mourinho as United went crashing out of the Carabao Cup.
Rookie Derby chief Lamps had a trophy-laden spell at Chelsea under the Special One.
And last night’s penalty shootout win was just as special for the Championship side’s new manager.
Phil Jones’ dismal effort saw United crash after a marathon shootout.
But Derby deserved to win this third-round tie in normal time after Jack Marriott’s header put them 2-1 up on 85 minutes.
The rested Paul Pogba had already left the ground when a Marouane Fellaini header five minutes into injury time took the tie to penalties.
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But Derby netted all eight of their kicks to go through.
United had started well enough, scoring after just three minutes through a cracking move. Ashley Young released Anthony Martial down the right and when he crossed Romelu Lukaku flicked the ball on for Jesse Lingard to set up Juan Mata for a sweet finish.
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Derby were full of ambition and came desperately close to equalising in the 53rd minute, but Sergio Romero pulled out a stunning save to stop Harry Wilson’s shot.
There was nothing he could do about Wilson’s next effort just before the hour.
Young conceded a free-kick 30 yards out and there were echoes of Cristiano Ronaldo the way Wilson hit the deadball with swerve into the far top corner.
It got better for Derby and when David Nugent put Wilson clean through, Romero came out of his area and handled.
It was a straight red, Mata had to be subbed and former Derby keeper Lee Grant came on for his debut.
Grant was called into action in the 78th minute with a great reaction save to deny sub Florian Jozefzoon.
Then with just five minutes left Mason Mount’s shot was saved and Marriott headed home the rebound.
Fellaini looked to have saved United's blushes at the death by taking it to penalties but it was not to be.
Paul Pogba seen in the stands at Manchester United v Derby Carabao Cup match
Paul Pogba misses Marouane Fellaini equaliser as he leaves his seat in 89th minute of Manchester United v Derby Carabao Cup clash