Dunno about that, Bill. Think Gianluigi Buffon, Stanley Matthews, Roger Milla, Teddy Sheringham... Messi's role in matches as he ages has evolved into one of conserving energy, drawing opponents away from the action to leave spaces for others to exploit and producing those occasional moments of magic that elude all (almost) other players. I think a fit 39-year-old could still do most of that...