Thornton surplus to Black Cat requirements
The player has courted controversy in his brief career. His move from Tranmere Rovers three years ago gained notoriety because he opted to stop training with them and join Sunderland at the end of his contract - an independent tribunal was set up to decide a fee as he was under 23 years of age.
He enjoyed a lengthy run in the first team in the final months of Sunderland’s top-flight stay in 2003.