Derby reject Robert outstanding at Toronto
Carver said: "It's not about what players have to prove, it's about the fact they have so much to play for and offer.
"Newcastle fans know what Robert's ability is about. From what I have seen in the short space of time he has been here, he has some desire back.
"He has had a couple of wayward years and he actually seems to want to prove a point.
"He's not here on holiday, he's working hard and he's a great professional."