The Black Cats prised the Italian international away from Serie A champions Juventus in a £6.8million deal.
But the 28-year-old has only begun to shine in the last two outings, with the attacking midfielder netting in each of caretaker boss Kevin Ball’s two games in charge.
He is taking every opportunity to improve his grasp of English after former boss Di Canio said: "My players do not know English and cannot communicate."
Kevin Ball: “Giaccy has really worked hard in training and he’s one of the fittest guys at the club.
“He’s very eager and wanting to settle into the way we do things.
“He’s learning English all the time.
“Sometimes I say to him ‘do you understand?’ and I have that look from him as if to say ‘I really don’t!’.
“Then one of the other boys is brilliant and they’ll help to translate and get him to understand.
“He’s carries a little book with him because he wants to learn English and wants to fit in.”