Di Matteo says he is keen for his centre-back to get back to business after his court ordeal.
He said: "I have spoken to John and he seemed OK. He'll be joining us in New York.
"He's a strong character who just gets on with things and he's looking forward to being back with the boys.
"I have never been in court so I don't know how it must have felt for John but I guess he would rather have been on a beach than in a courtroom.
"He's faced many difficulties during his career. But he has learned and he has improved with experience and with the help of his family. Being a father has also helped him."