Draymond Green can literally guard all five positions. You can probably count the amount of NBA players who can do that on one hand.
Steve Kerr played him at the freaking five, in overtime, during game one, and they completely dominated. The Warriors defense ranked #1 in points allowed per possession, and Steve Kerr and everybody else within the organization were pretty vocal about crediting much of that to Green. If you think Thompson is a better defender than Green, you're lost.
His passing skills make him a plus at the other end, too, and would in most systems. Is he LaMarcus Aldridge? No. But it is no coincidence that the two best offensive teams in basketball - the Clippers and Golden State - both feature four men with extremely good passing skills. Everything in todays league is geared towards pick and roll, and the best way to aggressive defenses - particularly when you're trying to corral a wizard like Curry - is to punish them with passes to the weak side on rolls.
I don't know how any of this relates to Winslow - he is nothing like Green.
@walker11 is correct that he is perfectly suited to be a three and D guy, the question is whether you want to take a three and D guy in the top five. Then again, he's like nineteen...I'm sure he can be more than that in time. Kawhi Leonard was drafted as that sort, and he's since become one of the best players in the league.