Drama, excitement and passion are three words used to excess in the FA Cup, but if there was any doubting the meaning of any of them then this Old Trafford tie proved a crystal clear explanation.
If memories of Manchester City's heroic win at Spurs in their fourth round replay will live forever in Blue hearts, then this fifth round success will grow and grow in Red folklore.
Reduced to ten men after 37 minutes by the dismissal of Gary Neville, United drew strength from adversity to withstand an early second-half onslaught by City and knock their neighbours out with three goals in a scintillating nine-minute spell.
Gary Neville had only himself to blame for being sent off.
As he charged into the City box in pursuit of brother Phil's pass, he was blocked by a perfectly good tackle from Michael Tarnat.
The prostrate Gary Neville appealed for a penalty, and when it was turned down by referee Jeff Winter, he beat the ground in anger and frustration.
When he got to his feet, he confronted angry City players and an eyeball to eyeball confrontation with Steve McManaman ended in him butting the former England international.
Scuffles turned into a brawl with several players involved and, when events calmed down, Gary Neville was first shown a yellow card for ungentlemanly conduct and then a red for violent conduct.
City's Joey Barton, who pushed Gary Neville as feelings ran high, was booked for his part in the proceedings.
But, as with City's magnificent recovery at White Hart Lane when the ten-man Blues recovered from a 3-0 half-time deficit to win 4-3, United drew on their reservoir of raw spirit.
After an opening half-hour of little more than sparring, United opened what proved to be this amazing box of FA Cup tricks in the 33rd minute.
Gary Neville found Roy Keane midway inside the City half. The Irishman worked the ball on to Ruud van Nistelrooy, whose delightful pass with the outside of his boot found Ryan Giggs on the left side of the box.
Giggs produced the perfect low cross into the six-yard box and Paul Scholes nipped in between City duo Claudio Reyna and Sylvain Distin to slot his right-foot shot home from close range.
City had two chances to equalise after Gary Neville's dismissal.
In the 44th minute, McManaman threaded the ball through for Robbie Fowler on the left side of the United box and his effort was well blocked by Tim Howard.
United's American goalkeeper produced an even better save seconds later when he clawed away Reyna's vicious goalbound shot from 20 yards out.
Howard was to prove the pivotal figure in the game for the opening 17 minutes of the second half.
City, trying to exploit their one-man advantage, pushed on wider on the right in an attempt to stretch United.
In the 52nd minute, Antoine Sibierski's superb ball from the left found Shaun Wright-Phillips free 12 yards out on the right side of the United box.
Wright-Phillips hammered in his shot, but he was denied by a brilliant save from Howard.
Six minutes later, Howard produced an even batter stop, hurling himself through the air to fist away Barton's blistering drive on the right side of the penalty area as the City man latched on to Richard Dunne's cross.
Forward came City again, only to be denied by Howard for a third time after 62 minutes.
Fowler picked out McManaman free on the left side of the United box, but his crisp drive was beaten away by the magnificent Howard.
United must have realised that they could not sit back and soak up relentless pressure and they launched a Red backlash.
In the 71st minute, Cristiano Ronaldo centred from the right. Giggs missed the ball at the near post, but van Nistelrooy thundered in at the far post to fire the ball home right footed from close range.
City were caught cold yet again two minutes later when United made it 3-0 from a glorious move.
Scholes found Quinton Fortune on the left side of the City box and the South African took the ball to the by-line before crossing into the centre.
Giggs collected the ball and got in a fierce shot which was well saved by City goalkeeper Arni Arason, but Ronaldo was well placed to collect the rebound and fire it right footed into the roof of the net from close range at the far post.
City pulled a goal back five minutes later when Distin's header was lashed home by Tarnat with a ferocious ten-yard left-foot volley on the left side of the United box.
But any thoughts of repeating their White Hart Lane feat were ended two minutes later.
Giggs floated over his free-kick from the right which was met by Roy Keane at the far post. Keane's header looked goalbound on its own, but van Nistelrooy made sure when he crashed the ball in right footed from close range.
Despite the scoreline, City were to give the Reds a scary finale.
In the 85th minute, Fowler scored with a quickly taken left-footed chipped free-kick from 25 yards.
Hope sprang eternal for City as Sibierski twice went close with headers and Fowler missed a glorious chance from close range.
But there was to be no second great escape for City as St Valentines Day brought only Red noses and the Blue's lady luck blew a goodbye kiss to their FA Cup dream.
After the match, United manager Sir Alex Ferguson said: "We could have been three or four goals up by the break. It was a really good performance.
"The sending off changed the nature of the game, but we were able to counter-attack and kept our discipline and patience.
"Gary Neville deserved to be sent off for the clash of heads, but if he had been booked earlier, that may have taken the sting out of events. The sending off was out of character.
"City came at us for 15 minutes after the break and Tim Howard made some vital saves, but we kept possession well and took our chances on the counter-attack." City manager Kevin Keegan, who must have suffered mixed emotions on this his 53rd birthday, said: "We created a lot of chances, but Tim Howard made some outstanding saves with the one from Joey Barton exceptional, but there were also some bad misses.
"United are a quality side and stuck their chances away well. I told our lads at half time this was a great opportunity against ten men, but we were not able to take it.
"I cannot complain about our creativity - we created eight decent chances and there were many plus points, but if you don't take your chances you can't expect to win games." Man of the match - Tim Howard The game definitely went Howard's way, with United's American goalkeeper making a string of brilliant saves - the three at the start of the second half proving the turning point in a match which lived up to all expectations.