I don't think his defense will improve much (due to physical limitations). But an area he could improve is his passing.
Vucevic is a skilled scorer who can score away from the basket as well as in the post but he does himself and his team a disservice with his below par passing. Especially from the high post where if his shooting was combined with above average passing, Vucevic could become one of the best high post facilitators in the league.
But he continues to show a level of disinterest in this area.
Vucevic is only out for himself. He doesn't play for his team or teammates. He doesn't make players around him better. He is selfish and plays low IQ basketball.
how bad is his passing really? statistically he isn't bad at 2.5 apg in 27 mpg and an AST% of just under 17. Doesn't turn the ball over much at just 9.2 TOV%
Even with his slowness he still has by far the best DRTG on the Magic at 99. Biyombo at 102 is next lowest.
It is not so much that his passing is bad. It is that is more middle of the pack.
It is a general reluctance to let go of the ball at times (goes through spells of being a black hole) and an inability to facilitate an offense through the high post (lowering the value of his jump-shooting ability).
I see passing as a key component of his game given:
* bad one-on-one defense
* bad team defense
* good but unexceptional scorer
For Vucevic to overcome that bad defense, he needs to make more of an impact on offense.
Now, if Vucevic was an efficient 25-30ppg type scorer with average passing, I wouldn't worry so much about his passing. But as a good scorer (3rd option type of a strong team), I view his passing -- his ability to facilitate an offense - I view that as a key to making it worthwhile for a strong team to give him 30+mpg despite his defensive deficiencies.
For his offensive value to be high enough that you will put up with his lousy defense -- which I do not currently believe it to be.