The midfielder has turned down a new contract offer this summer.
The Italian told the Sunderland Echo: "I've already spoken to him twice and he's done very well.
"He's a genuine guy with a fantastic attitude. Also, he's got quality too.
"He has to make clear what he wants to do in the future because if one player has it in his brain to leave, it is difficult.
"But he's got to keep going and keep behaving like he is. He doesn't look like he's having any difficulties. He's one of the most positive young players we have got. I'm very happy with him."