It marked the former Arsenal star's first goal for the Bianconeri.
He told TMW: "I am very happy to have scored my first goal and it was even more important to bring these three points home.
"Differences between Serie A and Premier League? I think it will take a few games to figure it out. For now I am happy for today, it was a beautiful moment for me.
"My favourite position on the pitch? The one in which I played today, as a number 8. A box to box midfielder."