"I will keep playing as long as I enjoy it, I am fit and the manager wants me," he has told the Sun newspaper.
"If one of those three things stops, I will consider retiring. It could be at the end of this season.
"I am at the end of my contract in May so we will see. At the minute there hasn't been any contact with United.
"I am as fit as I ever have been. The only difference is recovering from the game."