Press Association Sunderland boss Paolo Di Canio has urged Jack Colback to make a decision over his future after he rejected a new contract. The Italian told the Sunderland Echo: “I’ve already spoken to him twice and he’s done very well. He’s a genuine guy with a fantastic attitude. Also, he’s got quality too. “He has to make clear what he wants to do in the future because if one player has it in his brain to leave, it is difficult. “But he’s got to keep going and keep behaving like he is. He doesn’t look like he’s having any difficulties. He’s one of the most positive young players we have got. I’m very happy with him.” Colback has played much of his recent football for the Black Cats at left-back, and Di Canio’s search for a specialist this summer is ongoing. However, the manager wants his full-backs to adopt a more attacking approach next season and believes the Tynesider could be suited to the task. He said: “Now we are playing in a different way, he’s started to understand that as a left-back he becomes like a winger. “With the system we are going to use this year, both full-backs often during the game will become wingers. He’s going to enjoy it.” The 23-year-old midfielder, who has a year remaining on his existing deal, has turned down the club’s offer of an extension and his future remains uncertain less than three weeks before the start of the new Barclays Premier League season. Di Canio has been delighted with the academy graduate’s contribution during his time on Wearside, but having held discussions with the player, is keen for him to resolve the situation.