The details are outlined in a report from Diario Sport, who build on reports from Gazzetta dello Sport in Italy that the Chilean midfielder has agreed terms with the Italian club.
The Chilean international has had long-standing links with a move to the Italian club, where it is thought that he is keen on a reunion with his former Juventus boss Antonio Conte.
However, the latest report adds that the two clubs are yet to reach an agreement and whilst the Blaugrana will not allow Vidal to leave on a free transfer, they are likely to demand a fee below his €20m clause.
The central midfielder looked set for Inter in the summer of 2018 until the Blaugrana swooped in late to sign him from Bayern Munich.
Vidal had won eight successive league titles across three different clubs before the Blaugrana fell short in this season’s La Liga title race.
He is set to be one of a number of experienced high-earners to depart this summer with Ivan Rakitic joining Sevilla and the futures of Luis Suarez, Lionel Messi and Jordi Alba also unclear.