To understand the current contractual situation, one needs to understand the PSG project.
When club president Nasser Al-Khelaifi made his first media appearance following Qatar Sports Investments' (QSI) 2011 takeover, he insisted that the new enterprise wasn't concerned with signing existing superstars like Messi, but trying to unearth the next generation of gems.
And yet PSG still went out and picked up the likes of Zlatan Ibrahimovic and David Beckham to boost their prospects of success on and off the field.
Al-Khelaifi's commercial goal was to turn the club into a household name across the globe, like adidas and Nike, as underlined by PSG's partnership with Air Jordan – a deal he masterminded in an attempt to capitalise on the huge interest in basketball in the North American and Asian markets.
He also looked to the NBA for inspiration when it came to catering for and communicating with fans at the stadium. Al-Khelaifi closely observed what would happen at half-time, how they were selling food, how they would take orders, what they were wearing, whether fans could order from their seats.
Those close to him say he is obsessed with the smallest details and compare him to a sponge, constantly soaking up information, always pushing PSG to replicate the field-leading work being done elsewhere or, more often than not, asking whether they can do it better.
PSG also view themselves as 'the club of the new generation' because of the way in which they have tapped into the tastes of younger people. Ten years ago, for example, they had 500,000 followers. That's now shot up to more than 140 million.
PSG feel they are connecting and engaging with younger football fans in very different ways to other clubs. They target specific markets in specific ways. For example, in Japan, where they have three standalone stores, they work with local designers to produce high-quality gear that appeals to Japanese youngsters.
Al-Khelaifi, though, remains adamant that PSG are a French institution first and foremost. In meetings with Nike, he has been known to request the addition of symbols or flags related to France or Paris to remind everyone of this global brand's roots.
He even demanded that the food provided in the VIP area at the Parc des Princes come from the very best French caterers. When he hosts dinners, meanwhile, he chooses both the restaurant and the chef. Again, everything needs to be perfect and to reflect the very best that France has to offer.
The net result is that more and more celebrities are turning up to games wearing club merchandise, and, not because they've been paid to promote PSG – something the club says it never does – but because they 'like' the brand.
InstagramHowever, the importance of superstar signings simply cannot be overstated because, as even PSG have admitted themselves, they cannot boast the same history or pedigree as the traditional super-powers of European football.
They did not start out with anything like the same global fan-base, so they had to recruit high-profile players to draw attention to the Parc des Princes.
As a big fish operating in a small pond, they also needed European success to give credibility to the club. Ligue 1 titles were no longer enough for a team with a budget that dwarfed all of their rivals in France.
However, while their spending sprees sent shockwaves through the world of football, Champions League success continued to elude them (Al-Khelaifi promised they would lift the trophy inside five years), they decided to go nuclear.
In the summer of 2017, PSG signed both Neymar and Kylian Mbappe for record-breaking fees, believing that the pair would elevate the club to a whole other sporting and commercial plane.
It nearly worked, too, with PSG narrowly beaten by Bayern Munich in the final after establishing themselves as one of the biggest clubs in world football.
However, after a dire 2020-21 season which exposed obvious flaws in their policy of investing too heavily in a select few superstars, PSG doubled down, by signing the best player in the world.
Messi may have been free but he arrived on a colossal contract...