If Lionel Messi wasn't already inconsolable at Barcelona's recent turmoil, then an injury-time defeat to Athletic Bilbao will have done nothing to improve his mood.

Quique Setién's side are out of the Copa del Rey following Sergio Busquets' late own goal, though that is arguably the least of their problems right now. 

For the first time in years, there are very real concerns that Messi could leave Camp Nou at the end of the season following his high-profile row with Eric Abidal. 

The Argentine hit out at the club's sporting director in an Instagram post earlier this week for claiming the players hadn't worked hard enough under Ernesto Valverde. 

Barcelona's concern over the fallout was such that Abidal was called in for talks with president Josep Maria Bartomeu and may yet lose his job. 

The thought of the six-time Ballon d'Or winner in any other domestic shirt remains unthinkable for many.

At most, there are a handful of clubs who boast the resources to make that a reality should he decide to move on. Manchester City are one of them. 

While the rumour has never quite gone away, and has at best seemed an unlikely pipe dream emanating from the Etihad, The Athletic report that there are those within the club who now believe they have a genuine chance of pulling off the free transfer of the century. 

A clause in the 32-year-old's contract would allow him to leave Catalonia for nothing this summer and, contrary to some reports, it does not just apply to non-European suitors. 

So how did it come to this? 

Barcelona's demise 

Barca haven't won the Champions League since 2015 and are no longer atop La Liga either. Remember this famous image? Failure on the European stage could come to taint the latter years of Messi's career, no matter what he achieves in Spain. Messi is reportedly angry at Barcelona's shortcomings and now fears they cannot offer him the "sporting project" he wants for the remainder of his playing days.

In 2016, it's said that Messi was impressed by City's facilities while in England with his national team. Around the same time, he called his old boss Pep Guardiola and admitted he'd like to play for him again. 

However, the City manager could actually complicate the deal. He has stated previously that he thinks his former star man should retire at his current club and also fears how bringing him to City would damage his own reputation at Barcelona. Messi may also remember Luis Suarez putting him off living in England when he first considered upping sticks to join City. 

The other key man: Jorge Messi 

City first tried to sign Messi a decade ago and held talks with his representatives in Brazil. Ever since, they have maintained contact with his father, Jorge Messi, and that could give them an advantage. 

Financial Fair Play 

Let's face it, City have long been making a mockery of UEFA's system. The fact they look set to escape sanctions is only encouraging them and while the forward's wages are astronomical (in excess of £900,000-a-week according to some reports), that expenditure would be offset by not having to pay an initial transfer fee. 

There is, naturally, a bit of a stretch between the above cumulating to make a deal happen on paper and those circumstances actually transpiring. 

Think back to his international 'retirement' in 2016, when he was so unhappy it seemed there was no coming back from the brink. It wouldn't be the first time his moods have turned around. 

Yet the fact City have any confidence at all speaks volumes about Messi's unhappiness.