JUST when it was another night to drive Jose Mourinho mad – thank Heavens for Jesse Lingard.
Never mind Antonio Conte’s claims that the Manchester United gaffer was losing his marbles.
It was looking increasingly like one of THOSE nights, when – with just seven minutes left after a game of total dominance – United’s new goal kid on the block struck.
United had fired in 26 efforts without luck when Lingard took aim for one more from the edge of the box, as half time sub Romelu Lukaku teed him up.
And this time, at long, long last, keeper Scott Carson was left clutching thin air as it finally fizzed into the Derby net.
Heartbreaking for the Championship high fliers but totally deserved after running the show – and wasting every chance before then – for United.
Just when they were staring at the replay neither side really wanted, as well.
Sub Romelu Lukaku then ensured Mourinho's side will be in the hat for the fourth round draw when he scored in stoppage time with the Rams looking for an equaliser.
The woodwork, the fingertips of Carson, superstar strikers in the most wasteful form of their lives.
You name it, United went through it against the most dogged of Championship opponents. And they couldn’t even claim a weakened line-up as having played a part, either.
Mourinho had gone with an incredibly strong team. Then again, after the disastrous Carabao Cup loss at Bristol City, he was never going to do anything else.
Hence the presence of Paul Pogba in the line up – and boy, how Derby must have wished the Frenchman had been given a rest, the way he set off.
They simply couldn’t lay a glove on him at times, as his dancing feet left them rabbit-in-the-headlights transfixed.
Never more so than when Andre Wisdom and Tom Huddlestone looked on bemused as he teed up Jesse Lingard to fire one early effort over.
Pogba himself kept Scott Carson on his toes with a snapshot from nothing, and then rooted to the spot with another that curled a couple of coats of paint wide.
It was one of the few times Carson didn’t actually get a fingertip, hand or glove on most United could throw at him, though, with a string of inspired saves.
Old Trafford fans couldn’t have hated him more in his days as Liverpool No 1 than they did at times last night.
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The Rams keeper pulled off a jaw-dropping save when he flung himself right to turn a Juan Mata free kick behind.
But he left even that for dead with an even better stop as Pogba fired one in from fully 35 yards.
The one time he never got near it was the one time United should have broken the deadlock – and how they didn’t not even Marcus Rashford could explain.
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Mata and Luke Shaw combined cleverly to pick out the England striker totally unmarked, and barely six yards from the target.
He had to score. It was harder to miss. Somehow, though, he managed it, as he glanced a header against the foot of the post.
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A firm contact in any direction and it was a goal. A contact like he made minutes later to another Mata delivery – only for this time to fire it straight into Carson’s guts.
Not that Derby hadn’t really done enough to merit their good fortune. Their keeper was outstanding, their defending determined, gritty and dogged in the extreme.
And they could even have sneaked a half-time lead of their own, after going within an inch or two of scoring from nothing.
Johnny Russell’s delivery from the left was actually just behind Marcus Olsson, so it speaks volumes for the connection the Swede made in dragging a fingertip stop from Sergio Romero.
United were increasingly in need of something to slap the Championship promotion chasers into place. Something to give their dominance the breathing space it deserved.
Something to deflate the increasingly puffed up chests of their steadily beginning-to-believe it opponents.
Pogba had Carson on his toes again when he fizzed in yet another shot that the Rams keeper did well to block, and then clipped another sidefoot inches wide,
Surely it was only a matter of time. Surely United had to find a way through. Surely their dominance had to reap a reward sooner or later.
After all, this side had only lost United have one of their last 35 FA Cup games against lower-league opponents at Old Trafford - to Leeds eight years ago.
Rashford was the next to rattle a post, whipping in a drive from the right, before even Pogba got in on the act of miss-firing.
Lingard had the initial effort, again from the right, which Carson did well to push out. By now we had come to expect nothing less.
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Yet when it fell to Pogba, lurking unmarked on the penalty spot, he had to bury the rebound, even though it did come at him at pace.
Somehow, though, he fluffed his first time return and the ball bobbled wide of the target and the whole of Old Trafford stared in disbelief.
It was going to be one of those nights after all. It was stalemate all night long….until Lingard drew back his right boot and fired that one deadly arrow.