Since his £20m move from Aston Villa in July 2011, the former Middlesbrough winger has failed to impress and has now been told he can leave.
"The manager has said I can leave if I want to," he said. "I think it's just the nature of football, the old cliche about it being a funny old game is true.
"I've played for a long time and there are spells when you can be in and out of any side. At the minute I'm trying to play as much as possible.
"If that doesn't happen I am at an age where I cannot be sat around. I need to play and the manager understands that.
"That's how the situation is and we will have to see what happens in January or in the summer."