Give over, Mick. He's an athlete; light as a feather with two strong legs. He's quite capable of tracking back occasionally without sacrificing his attacking impact.
We don't need 11 defenders, when he's tracking back he's at the wrong end of the pitch to do damage. I'd rather have him as an outlet for when we do try to go forward, as rare as that sometimes is.
When I think about the most effective wingers I've seen In PL, pretty much every one of them has been prepared to track back. Why should he get an exemption? He's shown he can be incredibly potent when his attacking responsibilities are compounded with defensive aspects.