If he cleans up his handle and learns how to hit a layup and hits the gym he can be a bit of a poor mans Marcus Smart.
A poor man's Marcus Smart is a guy who plays in Europe.
What will hurt Purvis is that he's a 3 and D guy who isn't quite tall or long enough to be a 3 and D guy and maybe not a good enough shooter, either (though he has shown the range). It will also hurt him that he isn't particularly good at dribbling, can't create, and can't finish.
But he can defend and that will give him a shot - I'd rather head into the summer league as a guy like him, who has the athleticism to play at the next level, than a craft guy who can score but is DOA on defense. All it takes is a hot stretch of games from behind the arch to play himself into consideration for a roster spot.