When talking about Fab's ceiling consider these things.
Size = True 7ft, long wingspan, big hands, frame to support lot of muscles. 10/10
Athleticism = good elevation and quickness, excellent footwork and timing. 9/10
IQ = Difficult to evaluate, just learning the game. Good vision, good defensive instincts, plays within his limits. 6?/10
Motor/Attitude = Good energy, very coachable, liked by his teammates, can take a joke. 10/10
Skills = Excellent shot blocker, takes charges well, good passer, average rebounder, good shooting mechanics but needs more reps. 5?/10
His IQ will determine how far he will go. His skills will improve. He will continue to develop his fundamentals. But how much of the Xs and Os he can master will be his only limit.