The veteran Chile midfielder arrives from Besiktas.
He told Sky Italia: "I have been in Turkey for two seasons. Despite what they say, it is an important championship. I wanted to prove that I could still be competitive and do it in Italy.
"(Rodrigo) Palacio is a friend and a great player. I am happy to come back and play with him. (Sinisa) Mihajlovic is a warrior, he will beat everything."
He added, "Great player, he can give a lot. If he comes, he can be a good buy for Inter."