I'm not going to call him lazy or question his work ethic because I have no idea. And I give him credit for being willing to take a charge and being tall with long arms.
I DVR'd all the Boston summer league games and watched them twice. After the first game I wrote off Abromaitis from my watch closely list for second viewing and kept an eye on Olynyk, Mitchell, Pressey, Fab, and Iverson during my second watching of each game.
Fab just doesn't have it. The second anyone puts a body on him he doesn't move. He is the anti Sullinger. When a shot goes up Sully will turn his body sideways, try to slip through cracks, and push his way to good rebounding position. Melo doesn't move. He stays right there and hopes the ball bounces over your head.
He went up for a dunk and some white 6-10 German looking guy absolutely stuffed him at the rim. This wasn't some athletic 6'11" guy with long arms, but an earthbound, muscled up guy who absolutely stoned Melo. Fab goes laughing back up the court.
He just doesn't have "it". You have to want to be good. You have to push yourself. Look at Shav. Much smaller guy but has "it" to rebound. Every ball out there was his and he was going to go get it. With Fab its... its just painful to watch honestly. A guy who is fighting for a spot in the NBA without the motor to do the one thing he has to do, rebound.
He got blocked a couple of times... so what? Who cares? It happens to Dwight Howard and Lebron James too.
Do people realize that we are talking about someone who played 2 years in high school, 2 years in college and 1 year in the D league? Just try to imagine how little basketball that is. Of course he's not going to be confident. That takes a lot of time. By the way, he eventually become a defensive force in all levels that he had gotten minutes in.
Everyone has their skills. Shavlik is a great re-bounder, Fab Melo is not. That doesn't mean that Fab doesn't have "it." Melo is still developing his skill set. He is very good at steals, blocks and taking charges. He's pretty effective in defending the pick and roll. Fab has excellent passing ability. He is working on a mid range game and a hook shot. He may never become great, but he will get better at setting picks and boxing out.
Fab hustled a lot when he was on the floor. One play stands out (against Indiana) he fought for an offensive rebound, dived in the floor to save it from going out of bounds to Olynyk, who missed a jumper but Mitchell (or Fells) gathered the miss for a nice floater. Melo's hustle gave us those two points.
Just because your teams want you to doesn't mean you can become great at something that falls outside of your skill set. Natural talent plays a role in what you are good at. I'm sure Fab works very hard at rebounding, but that doesn't mean that he can become a great re-bounder.
The Celtics did not draft Fab for his rebounding prowess. They drafted him for his impact on the defensive end. That means, challenging shots, getting deflections, blocks, steals and charges. He will also work on other aspects of the game like rebounding, shooting etc.
There is a lot of room for growth with Fab. That is why his ceiling is so high. As fans, we have to be patient.