According to sources who have told Football Insider, Oxford United are interested in signing Sunderland defender Zak Johnson. The 21-year-old is also being pursued by League One rivals Wigan Athletic and York City, where he spent last season on loan and was a key player in their National League title victory. Johnson's contract with Sunderland expires at the end of the month, and while he appears on their retained list, he is expected to depart as a free agent. It is reported that Sunderland are prepared to let the centre-back leave as he is not in manager Regis Le Bris's plans and would struggle for first-team opportunities.