Not a good sign at all. Once an athlete considers retirement or has the thought of retirement creep in his head, it's pretty much a done deal. The grind of a season is taxing both mentally and physically. Sure in August he feels fine and wants to play, but come January or February when his body is bruised and battered (and we all know it will be) that's when the question of "why the hell am I doing this" will come up.
Several former pro athletes, most notably Charles Barkley, have mentioned that once you start thinking about retiring or retirement, you're pretty much done.