They surrendered their remarkable unbeaten run without so much as a whimper.
This was Manchester United at their worst, well beaten by a Leicester side full of energy and desire which the visitors were so clearly lacking.
Incredibly, this was United’s first away defeat in a domestic game in 14 months, a run stretching back 29 games to January 2020 when they lost at Liverpool.
That takes some doing and is a clear sign of progress under Ole Gunnar Solskjaer and yet defeat this time means they kissed goodbye to one of their two remaining chances of silverware this season.
United have such a wonderful tradition in the FA Cup, lifting the trophy 12 times and another season finishing empty handed again would raise all of the familiar questions about Solskjaer.
Of course United are still in the Europa League, they could finish in the top four and you could blame their listless display at the King Power on a long, gruelling trip to Milan in midweek.
But it also highlighted United’s lack of options, lack of a squad and if the first XI do not start then they are simply not good enough and that seems pretty inexcusable for a club of their size.
This is now a wonderful opportunity for Leicester, they will face Southampton in the FA Cup semi-final and of course their 9-0 win at St Mary’s in October 2019 still seems fresh in the memory.
But this is also about the progress that Brendan Rodgers is making at the King Power Stadium because they enjoyed the greatest chapter in the club’s history by winning the title in 2016.
Now, five years on, they are 90 minutes away from the FA Cup final, they have a shot at another fairytale.
Rodgers has guided them to their first FA Cup semi final since 1982 and has got Kelechi Iheanacho playing consistently and brilliantly.
Iheanacho has been something of an enigma until this season, good in flashes, more super-sub than starter and yet here he was again scoring twice and providing the assist for Youri Tielemans.
That goal summed up Leicester’s drive and energy as they had too much for United, tearing through their leaden-footed midfield with Fred and Nemanja Matic looking as if they were running through treacle at times.
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In fact, it was only when Solskjaer threw on the cavalry late on - bringing on Bruno Fernandes, Scott McTominay, Luke Shaw and Edinson Cavani with 25 minutes left - that they eventually made a fight of it. But by then, it was too little too late.
Leicester were far better from the start and United gifted them the opening goal after 25 minutes. Fred dropped his back pass short, Iheanacho nipped in and rounded United keeper Dean Henderson and slotted into the empty net.
In fairness, United levelled with a brilliant goal before half time. Paul Pogba sent over a low cross, Donny Van De Beek provided a terrific dummy and Mason Greenwood swept home his first goal in two months.
But the second half was all Leicester. Tielemans restored their lead after 52 minutes after a neat one-two with Iheanacho which embarrassed Matic who was chasing shadows.
Tielemans was given so much space and time to run through it was embarrassing before he arrowed a low 20 yard shot into the bottom corner.
Jamie Vardy missed a gilt-edged chance even before Iheabacho wrapped it up after 78 minutes, Marc Albrighton’s free kick found Iheanacho unmarked at the back post and the Leicester striker headed home.
Incredibly, this was only Leicester’s second win over United in 26 previous meetings spanning 23 years and it must also go down as their most important because it is a passport to silverware that Solskjaer is still sadly lacking as United boss.
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