The midfielder missed his country's final group game against the Netherlands due to a persistent knee problem.
Despite doubts over his availability, Sampaoli has revealed that the 27-year-old will feature against the Brazilians in Belo Horizonte.
"Arturo is ready to play," he told FIFA.com. "Towards the end of the season with Juventus, he played in the Europa League when he was only 30% fit. Today he is still nowhere near 100% but we all agree that he has to play."
Chile head into this evening's match having finished in second place in Group B.