The former Millwall man joined United back in January from Gillingham for a undisclosed fee and after coming on as a substitute scored on his debut in a 3-3 game at home to West Ham United.
"I've had a good chat with Paul and we have agreed that him coming up here has not worked out," Warnock told sufc.co.uk.
"He feels, and I agree, that his opportunities will be restricted this season.
"Paul is a good pro, but for one reason or another it has not worked out."