The player's agent Viktor Kola told The Journal: "Radoslav would be interested in a move.
"It would certainly be a solution he would welcome. He knows the history of the club so I believe that from his perspective there would certainly be interest if Sunderland did make a bid.
"He realised that he can handle the level of English football and could make an impact in the Premier League.
"He enjoyed his time in England and ideally wants to come back. If Sunderland made an offer of course he'd be interested."