Ronaldo wanted to leave the rags the season they won the champions league. Is he the best out and out left winger we have? Have we missed him this season? Do you think he'll play shit because he hasn't signed a new contract? If he's fit, gets a couple of games and does well, i'd fucking start him and try and win this competition.
Ronaldo is possibly one of the most driven, self-serving footballers the game has ever seen. If Sane had Ronaldo's attitude he'd be undroppable and end up the best in the world within a couple of years. Ronaldo is absolutely obsessed with winning at all costs, and that's what gives him his edge. There's nowt to suggest Sane will be anywhere near as bloody-minded if his heart is elsewhere. I get the point you're making, but it's a stretch when you're comparing him to a freak one-off.
Edit - fwiw, I think Sane will come back and play the odd game, but it'll be like last season. He'll be a rotation player most likely.