Oscar struggles to score against taller, longer players. Every NBA team will have taller, longer players. He will be severely offensively limited at the NBA level, both because of this and because even if he can hit jump shots he has a VERY slow release and NBA defenses will rotate to defend that.
Pick and roll is a staple of NBA offense, and NBA bigs MUST be able to defend pick and roll with NBA guards. Those who can't, get played off the court. There are going to be legit questions how Oscar can defend the pick and roll with NBA guards and more mobile NBA bigs.
He may get drafted 2nd round, he may make a roster and be a reserve player, but he's just not a high demand NBA guy.