I was able to scout Greene this year, and I was actually looking at him with my mock draft anywhere from 12 to 17 or so.. He's definitely top 20 in talent.
Below is my writeup on Greene I did near the end of the college season.
"Greene has tremendous height at the SF position and athleticism which will create matchup problems for anyone attempting to guard him whether it be a SF or a PF. Donte can hit open shots out to NBA 3pt range with ease and can also create his own shot off the dribble. Greene has shown he can get to the line when he wants, but seems to shy away from contact and shoot jumpers more so then driving into the lane. Green isn't a bad rebounder as his stats might indicate. It has more to do with him not being in position on the offensive end to get the rebound. His defensive rebound totals matchup with any tweener forward in the draft so as long as he drives to the basket more then he shouldn't have a problem. Defensively Greene is not a liability, but he isn't a stopper either. More of a weak side help defender. Greene also needs to learn that he has four other teammates on the floor. He tends to hold the ball too long before taking a shot."