Lionel Messi shocked the world on Tuesday when he announced — via burofax, no less — that he wants to leave Barcelona after 20 years, opening the door for teams like Manchester City, PSG, and Inter Milan that have long lusted over the prospect of reeling him in.

Powerhouses around the world have seen this scenario before. Lionel Messi has been unhappy before. He's wanted to leave before and he's been rumored to land with various football supergiants before — but the rumors have never been this strong.

Similar rumors were there in 2018 when a 3-0 loss to Serie A side Roma sealed Barcelona's fate in the UEFA Champions League quarterfinals and there again in 2019 when eventual champion Liverpool thrashed them 4-0 at the Camp Nou for one of the worst international defeats in team history.

Those previous embarrassments would seem minute after Bayern Munich won decisively earlier this month with an 8-2 result that will be seared in the minds of every Blaugrana fan.

That collective embarrassment was also etched in Lionel Messi's mind, as it has now been one letdown after another. This Champions League loss was also coming on the heels of Barcelona letting that La Liga title slip away after the restart, to bitter rival Real Madrid, no less.

The writing on the wall was there, and it was only time Messi vowed to leave after a series of disappointments with a club that has failed to be the dominant powerhouse it once was in its heyday.

But is a move to teams like Manchester City, Paris Saint-Germain, and Inter Milan realistic at all?

First, let's look at what's on paper:

Barcelona won't make this easy

Ronald Koeman, Lionel Messi, Josep Maria Bartomeu

Despite Lionel Messi's request to leave the Camp Nou for a new venture, the club is looking at his contract, which stipulates he must request to opt-out by July 10 or else a €700 million transfer fee would apply for his services. While that date would have normally coincided with the end of the season, the coronavirus pandemic stretched Barcelona's end-of-season until August.

Even if Messi is technically allowed to leave after every season and before the new one begins, lawyers have told FC Barcelona that Messi won't win that war if it goes to arbitration.

Former Barcelona president Joan Gaspart (2000-03) believes Messi won't be able to leave on a free transfer this year. He spoke to Radio Marca after the fallout, noting the Argentine star is contractually obligated to follow that release clause, which would force interested clubs to pay that hefty €700 million fee for his services.

“I have seen the contract and it is very clear. The clause ended in June and there is no going back,” said Gaspart. “I prefer him to leave next year for free than to go for less than €700 million. The club rules here, not the player. The club has paid the players. And this is not a matter of money anyway, because there is a signed contract and that's it.”

Some see this stalemate as a war of attrition, and it very well could be — but the Argentine just wants to make a point: he's out and that decision is very much final.

Messi has no plans to complete his preseason physical exams or show up for training camp ahead of the upcoming 2020-21 season. Simply put, he's done with Barcelona after giving the board of executives enough chances to turn the squad around.

This isn't posturing from Messi's camp, it's a clear warning shot: I want out, whatever it takes.

Not many clubs can afford Lionel Messi

Lionel Messi
ClutchPoints

While Messi has been linked to clubs like Manchester City, Paris Saint-Germain, and Inter Milan, that €700 million transfer fee is downright impossible to pay, if not crippling for a club's finances.

Manchester City, for one, has to hope Barcelona comes to reason and greatly reduces its asking price for the Argentine to be able to comply with the Financial Fair Play rules.

Before he signed his new contract in 2017, Messi's release clause was €300 million (£270 million/$355 million) — a much more reasonable asking price, even if it is for the best player in the world.

In an apples-to-apples comparison, the Catalans received a €222 million fee for Neymar once he left the Camp Nou in 2017 to make his move to PSG. Messi's price tag would roof over that, but more than tripling it was a way for the club to clearly say he's off-limits.

Even in the event that Barcelona has a come to Jesus moment and decides things are too ugly to keep stalling, Messi's wages of €565,000 a week could also become a problem for a team trying to balance out its payroll and keep other valuable players around him.

Lionel Messi has to be willing to take a discount on his salary earnings, otherwise, he won't be able to challenge for hardware, which is the main reason why he's choosing to leave Barcelona.

Who has a realistic shot at signing Lionel Messi?

Lionel Messi

It's still too early in the game to determine a clear winner. This saga will be a game of chess that must be won move by move, but Manchester City has a head start.

Messi's strong relationship with best friend Sergio Agüero and former manager Pep Guardiola greatly helps his move to a different league after being part of the same club for 20 years.

Guardiola still thinks the world of Messi. If that wasn't clear, watch him pick him as the best striker he's ever coached or played against — even after he made the move to Manchester City to manage Sergio Agüero:

Manchester City also has the financial means to pay a player of his caliber and surround him with other talents to build a winning machine. How that looks on the pitch is another story altogether.

Placing Lionel Messi in that same attacking playmaker role would conflict with what Kevin De Bruyne does for the Cityzens. Moving the latter to either flank would eliminate some of his best skills.

De Bruyne's field of vision is unparalleled and his long balls traced across the pitch, timely runs forward, and his technical ability with set pieces are all things that Messi does well, if not better than De Bruyne.

According to Guillem Balague of BBC, Messi and Guardiola have yet to speak on the possibility of his arrival.

In short, Manchester City won't move heaven and earth for Lionel Messi unless he's able to leave for free, which would surely change that conversation.

As for Paris Saint-Germain, the club told Balague there is no interest in Messi, despite comments from Neymar's agent, who said it would be easier for Messi to move to PSG than for Neymar to return to Barcelona.

Inter Milan is an interesting story. The Serie A side, which fell to Sevilla in the UEFA Europa League final this past weekend, was willing to do what it takes at first to make a move for Messi. However, even in the eye of the storm as Barcelona was eliminated from Champions League contention, the noise coming from the fashion capital of the world quieted down greatly.

Other prospective teams like Serie A champion Juventus have added themselves to the mix, along with Manchester United, which is never far behind Manchester City's potential moves.

Yet when it's all said and done, Lionel Messi will have to win a court battle to be able to leave for free or have Barcelona greatly reduce his transfer fee to be able to leave in 2020. Otherwise, it could be another year of waiting for all the aforementioned clubs and a lot can happen within a calendar year that could change Messi's ultimate trajectory.