When international transfers/loans take place there is a need for international clearance from the respective associations, but it would seem in this case that international clearance had not been granted.
It would appear that Ji Dong-Won was last season loaned from Sunderland to German Club Augsburg, returning to his parent club for the start of the 2013/14 campaign.
Milton Keynes Dons Football Club were only yesterday evening made aware that Sunderland had allegedly fielded an unregistered player in five games earlier this season, including the Capital One Cup second-round tie against MK Dons.
By the time the Football League were aware of the player’s ineligibility, Sunderland had already progressed to the fifth round of the Capital One Cup.
The Club acknowledges that the Football League board dealt with the situation as they saw fit and will not be pursuing the matter further.