Barella says he leaves proud of his contribution.
He posted to social media: “I tried to work my socks off to help the team achieve their objectives. I gave everything on the pitch, every time, from the first to the last minute, in every game.
“I gave and received a fair few knocks, I discussed with referees and argued with opponents. I celebrated, shouted, cried. Playing for Cagliari is all at once a pleasure, an honour, a responsibility: something that makes victories sweeter and doubles the weight on your heart in defeat.
“Aside from the personal satisfactions, I always put the team first. It was the only thing that mattered. It is Cagliari. It is the shirt: I tried to honour it with all my strength, and I think that I achieved that.
“Now a new chapter in my career begins, I am ready to fight and give my all for these new colours and new fans. I will always keep my land and its people in my heart with great affection."