England Under 20 international Blair Adams – allowed to convert his loan to Coventry City into a permanent move last week – leads the exodus.
Former Arsenal wide-man Roarie Deacon was only contracted to Sunderland until the end of 2012 and his contract has not been renewed.
Midfielder Adam Reed (right) is understood to currently be in talks with Portsmouth over a move there.
James Armstrong, son of former Sunderland midfielder Gordon Armstrong, has left and joined Hull City.
And Craig Lynch and Ryan Noble were both alerted about potential loan moves to Holland.
The loan moves to Holland will not go ahead but Lynch is believed to be considering a trial and potential full-time move to Sheffield United.
Both Lynch and Noble remain under contract but their Sunderland futures look uncertain to say the least.
O’Neill: “Blair is a good professional and a good player but he had reached the stage of his career where he needed to be playing games and we couldn’t guarantee him them here.
“This move is good for him and it will help his career to develop and if it does so, we won’t lose out as a club.”
Still at Sunderland are injured centre-halves Louis Laing and John Egan, while midfielder Billy Knott, whose season has also been blighted by injury, remains on the books.