To paraphrase a question supposedly asked of George Best in a hotel bedroom, where did it all go wrong for the FA Cup?

The answer remains the same: Manchester. There are two obvious salients to help chart the decline of the nation’s favourite knockout competition, and both involve decisions made in and around Old Trafford over the past couple of decades. The first was Manchester United pulling out of the 2000 event, with the shameless connivance of the Football Association, to visit Brazil instead in what we now know to be a hopelessly naive attempt to win votes for a World Cup in England.

Manchester City team selection was a slap in the face for the fans | Simon Hattenstone Read more

What seemed a poor decision at the time looks even worse from today’s perspective, particularly as United were not only the holders but defending the Treble. Few teams will ever get the chance to do that, and although the domestic cup is clearly the weakest element of the three titles, that it should have been the FA helping undermine the importance of its own competition remains scandalous.

The next big low point came almost a decade later, when United were beaten by Everton in a 2009 Wembley semi-final through fielding a weakened team. Everton would never have got past a full-strength United side, and failed to convince in the final against Chelsea, but Sir Alex Ferguson decided players such as Wayne Rooney and Cristiano Ronaldo would be better saved for Champions League challenges ahead.

This was not the first time Ferguson had made clear through team selection that the FA Cup was low on his list of priorities, and other managers had done the same by this point, yet disrespecting the competition at the semi-final stage was a new slap in the face. In the old days teams would never have done such a thing when they were 90 minutes from Wembley, but United already were at Wembley (pah!) and nothing could have demonstrated more starkly that the old days and the old ways had been consigned to history.

So all those accusing Manuel Pellegrini of perpetrating the worst ever act of vandalism on the FA Cup are wrong. Chelsea v Manchester City ought to have been the tie of the round and it was sad to see how it ended up at the weekend, but managers are paid to make decisions and there was not only logic but precedent behind Pellegrini’s reasoning. He might yet end up with egg on his face in either Europe or the Capital One Cup final this week – Ferguson’s careful husbanding of his resources in 2009 saw United squeeze past Arsenal in the Champions League semis only to fall short against Barcelona in the final in Rome – but when you have a lengthy injury list and three big matches in three different competitions in the space of eight days, then something has to give.

Those arguing that Pellegrini has turned his back on more attainable silverware are also being slightly unfair. In all probability the FA Cup would have been easier to win than the Champions League, in which City have generally struggled against the top sides. It would have been easy too for Pellegrini to concentrate on the domestic prizes in his farewell season, so as not to bow out empty-handed.

But the brief when Pellegrini arrived was to advance and improve the team in Europe, and he is doggedly sticking to it. City have never been in the last eight of the Champions League, and now they have a chance. Even if they don’t make it any further that at least is experience in the bank for the next manager to build upon. In the circles in which City are now moving, the company they are aspiring to keep, an FA Cup win by itself would not be a satisfactory return. Look at Arsenal. They are pleased with two successive FA Cups though not exactly delighted. Mostly they are just relieved the joking has stopped.

That is, of course, the trouble. Touching as it was to hear City fans complaining they fancied a day out at Wembley in May, the bottom line is that the Champions League and the FA Cup exist in the same space. If you are lucky enough to be involved in the first, you are unlikely to allow the second to compromise your chances. Occasional treble feats might suggest otherwise, though to win a treble you need to be the best team in your country by a considerable distance, and keep your best players fit through the business part of the season.

Facebook Twitter Pinterest Manchester City players leave the pitch after their 5-1 defeat at Chelsea. Photograph: TGSPhoto/Rex/Shutterstock

City are not in that situation, and it must be remembered that though United’s Cup final against Newcastle in their Treble year was something of a formality, the semi-final against Arsenal involved a replay, a last-minute penalty save and a prodigious winning goal. It could have gone either way.

Even so, the fact that everyone remembers Ryan Giggs’s memorable winner means the FA Cup was alive and well as recently as 1999. It still meant something then, because both Arsenal and United gave it everything they had. Then United pulled out the following season, and the decade that followed brought a succession of mostly drab finals – exceptions can be made for 2001 and 2006 – mainly because each one involved teams from the Champions League elite.

That expression, Champions League elite, is ultimately where everything went wrong for the FA Cup. In all the years when only the champions from each country contested the European Cup the two competitions happily existed side by side.

Things started to change from 1997‑98 when runners-up were first admitted, and from the millennium onwards up to four teams from the major leagues could take part. Check those dates against the perceived decline of the FA Cup. That’s where the glory went.

How could it ever retain its old status when the best four teams in the country were required to play bigger, more glamorous, more lucrative games at the same time? Now people are talking about switching to midweek or scrapping replays, when they should be looking instead at the insidious creep of the Champions League. Ought it really take a whole month to sort out the round of 16?

That’s eight separate match-nights, from 16 February to 16 March, or four whole closed midweeks, because Uefa will not tolerate any televised competition to its prestige tournament. Now the notion is even being mooted that slackers such as Manchester United should be allowed access through a Champions League wildcard. Keep an eye on that one. Nothing in the Champions League’s short history allows confidence that bad ideas that work in favour of big clubs will be rejected out of hand.

Too much of the debate over the past week has assumed it is the FA Cup that has become a problem. It certainly has a few problems, though its basic precepts of fairness, accessibility and opportunity ought to be celebrated rather than abandoned or adapted in the name of progress.

Especially if progress is represented by a competition that was designed to be elitist, self-enriching and disruptive. Stealthily invading space that belongs to others while refusing to make concessions of its own, the biggest problem here is the one hiding in plain view.