The Morocco international has impressed at the World Cup and is being linked with Liverpool.
Valcareggi told TMW: "He had to wait. He was very useful, now he also plays well.
"He is also a (president Riccardo) Commisso pupil, I think he will keep him.
"In June it could be worth 50 million (euros), now I would keep him. Americans don't need money, they need to win."