Bryan 'Pop' Robson has warned Sunderland midfielder Jack Colback about moving to Newcastle United.
He is one of a number of players who played for both teams and made a success of it but Colback would be the first for 17 years to make the direct swap.
"He is a tidy player - a very good player for Sunderland and I think he has really come on in the last couple of season," Robson told The Journal.
"It is a difficult move for him to go from Sunderland to Newcastle because he will have to prove himself to Newcastle supporters and Sunderland fans will obviously not be happy. It is a big decision."
