Messi slapped in a transfer request ahead the start of the season before withdrawing it after Barca refused to cave over demands he be granted a free transfer.
Indeed, Barca not only denied Messi's claims that his contract carried a release clause at the time, they also referred interested clubs - including City - to his €700m buyout clause.
A source told ESPN: "If Barça had let him go for €100m or €150m, Messi would be a City player."
And it's also been revealed the extent of which Guardiola pushed to bring Messi to England.
"Messi and Pep talked for hours," revealed another source, confirming reports of Guardiola having convinced Messi about joining City for the chance of winning the Champions League again late in his career.