Portuguese newspaper A Bola claims Messi is unhappy with a perceived lack of support from Barcelona as he's come under investigation by Spanish authorities for tax fraud.
And Manchester City are one of four teams monitoring developments, well aware of the player's gigantic €250m release clause.
Anzhi Makhachkala, Paris St Germain and Monaco are the three other teams credited with an interest.
Financial concerns would not be an issue for any of the four clubs, and the report claims an offer of €120m would test Barcelona's resolve this summer.
The four-time Ballon d'Or winner has publicly played down the tax fraud allegations but behind the scenes the report suggests he's displeased with Barca officials. He and his father have been accused of defrauding Spanish tax authorities of more than €4m by filing false returns.
The alleged hidden funds concern payments regarding Messi's image rights, which the authorities claim have been sheltered via of series of shell companies scattered around the world.
The 'lack of support' angle brings to mind concerns reportedly shared by Cristiano Ronaldo regarding his Ballon d'Or candidacy last year.
It's difficult to believe Messi - who has spent his entire career at Barcelona and is the club's record goalscorer - would be unhappy at the Nou Camp.
But while the allegations continue to linger over the Argentine, the report claims the four teams will keep an eye on developments.