The conclusion of Portugal's World Cup campaign would have felt familiar to Manchester United fans. It ended with Cristiano Ronaldo walking straight down the tunnel after a desperately disappointing defeat.

There was no magnanimous applause for the victors. No attempt to console crestfallen teammates. No show of gratitude towards the travelling supporters.

Because this wasn't about them. This was all about Cristiano Ronaldo. Just as it has been all along.

Before Qatar 2022 had even begun, Fernando Santos and Bruno Fernandes were showing visible signs of frustration with the press' preoccupation with the Portugal captain.

Ronaldo had even made an impromptu appearance at a media conference and implored journalists to stop asking his teammates questions about him.

Fat chance of that, though. Ronaldo was the only thing that anyone cared about. He was the story. Because he had made himself the story with a horribly ill-advised and dreadfully-timed interview with Piers Morgan on the eve of Qatar 2022.

The interview achieved its objective, of course. By eviscerating nearly everyone collected with United, he successfully forced the club into releasing him, which is what he had been pushing for since the summer.

However, it didn't go over well with some of his team-mates. Ronaldo received an unsurprisingly frosty reception from Fernandes, which he tried to pass off as good-natured banter.

However, when even Joao Cancelo appeared to take issue with Ronaldo in training, it became clear that all was not well in the camp.

Ronaldo had created an unnecessary distraction, a media frenzy that the Selecao really could have done without going into a tournament they had a serious shot at winning.

The hope was that once the games got under way, Portugal could quickly put the controversy behind them. However, that's when things took a surprising turn.

It's been clear for a few years now that time is catching up with Ronaldo, which is perfectly understandable. He is 37. He cannot do what he once did. He's admitted that himself. So, he ditched the superfluous stepovers to focus on finishing.

Such a basic approach was always likely to prove unsustainable in this modern era of high presses and fluid forward lines.

What's surprising, though, is just how quickly things Ronaldo's game has unravelled in recent months.

He scored 32 goals for club and country last season. He's managed just four since August, half of which came against Sheriff in the Europa League.

The decline has been as dramatic as it has been devastating. Like watching a legendary boxer get old in the ring overnight.

There was always a suspicion that he would prove a bad fit for Erik ten Hag's Manchester United, so it didn't come as a shock to see the Dutchman realise that United were better without Ronaldo in the starting line-up.

What we didn't expect, though, was for Santos to follow suit. At least not in the middle of this World Cup.

Portugal looked to have enough hard-working attackers, like Fernandes, Joao Felix and Bernardo Silva, to compensate for Ronaldo's lack of mobility.

However, during the group stage, it became glaringly obvious that Ronaldo was holding Portugal back.

He may have netted in their group opener against Ghana, converting a penalty that he had won himself, but he was contributing very little overall.

Worse again, he was no longer carrying the same attacking threat. His timing was off. He was being repeatedly caught offside. Even his touch was letting him down.

It was telling that he started against South Korea given Santos elected to bench most of his first-team players.

The hope was that Ronaldo was merely rusty after spending most of the final few months of his second spell at Old Trafford on the bench. The thinking was that the extra minutes might help him rediscover some sharpness.

Ronaldo instead endured a nightmare evening, playing a part in South Korea turning the game around by inadvertently setting up their equaliser.

When he was mercifully hauled off midway through the first half, he reacted with a petulant show of dissatisfaction with Santos. "You're always in such a f*cking hurry to take me off," he mumbled to himself.

Cue more unwanted media scrutiny for Santos. In truth, though, he may have welcomed the outburst. It presented him with a convenient excuse to drop his skipper for the last-16 showdown with Switzerland.

It was still a colossal call by Santos. It put him and his players under an enormous amount of pressure and yet they performed as if a weight had been lifted off their shoulders.

Ronaldo's replacement, Goncalo Ramos, scored three goals and set up another in his first ever World Cup start. There was, thus, no chance of a Ronaldo recall for the quarter-final clash with Morocco.

Indeed, he was sitting on the bench when Youssef En-Nesyri opened the scoring with the kind of towering header that Ronaldo made his trademark. There was even what looked like a reluctant nod of approval.

Santos' hope was that Ronaldo could produce something similar when subbed on shortly after the start of the second half. He remained a peripheral figure, having just 10 touches of the ball. He certainly tried his best. But Ronaldo's best is not what it used to be.

Again, there is no shame in that. Age catches up with us all. Plus he has, as Mesut Ozil pointed out, set records that will likely never be surpassed, while former Juventus team-mate Merih Demiral insisted: "He is the GOAT and will forever be. This changes nothing."

Only that's not really true, is it? His place in history is undoubtedly assured. He is Mr. Champions League. He has won five Ballons d'Or. No player has scored more goals in international football.

As he likes to say, his numbers speak for themselves.

But no goals in the knockout stage of the World Cup also tells its own story, and it's a tale of frustration and underachievement with a bitterly disappointing final chapter that won't be easily forgotten.

Ronaldo's World Cup legacy has undeniably been tarnished by this calamitous campaign, just like his reputation at Old Trafford before it, because we've seen similar displays of selfishness, petulance and unprofessional behaviour.

Even those that have portrayed his individualism and infantile behaviour as an inevitable side-effect of his single-minded pursuit of perfection stopped defending him after the embarrassing Morgan interview.

Qatar 2022, then, was meant to be about silencing the critics. He wanted to disarm those who had their "rifles pointed" at him; instead, he only provided them with more ammunition.

In that sense, this World Cup has been a sporting and public relations disaster for Ronaldo.

And he knew it too.

He was desperate to get off the field as quickly as possible against Morocco but the tears began to flow before he'd even made it off the field.

Ronaldo was well aware of the significance of the moment. "The dream ended," as he put it himself. It was all over.

Portugal's campaign in Qatar. His final shot at World Cup glory. And his claim on the title of the greatest of all time.

That was always going to be too much for Ronaldo to take, making a tearful walk down the tunnel as fitting a finale as it was familiar.