The Black Cats youngster sustained a horrific leg-break while on loan at Bradford City and is subsequently set to undergo surgery to correct the injury
The Republic of Ireland under-21 international sustained the injury just 13 minutes into the first half of the Bantams' victory against Plymouth Argyle on Tuesday November 20.
Speaking about the injury, Bradford City assistant manager Sam Perkin said that it is a 'heartbreaking' injury for the player and stressed that the focus was on aiding the defender's recovery.
"The minute he landed on the ground, we could all unfortunately see how bad the injury was by his reaction and the reactions of the players around him," Parkin told the club's official website.
"It is heartbreaking because he's a young lad who's come into the building only recently and done ever so well. He has been an outstanding young man - on and off the field - and he has been excellent in all of the games he's played for us.
"The main thing to focus on now regarding John, however, is that he gets all the right treatment he needs and that he recovers from this injury as soon as possible," he said.