Vucevic improved a lot defensively, especially since he was coached by Scott Skiles and then Frank Vogel. Awful defender his first four years in the league but has been steadily improving - last season he hustled a lot and was easily an above average defender, vulnerable in certain situations like switches, pretty good at closing lanes, contesting his man and of course a tremendous rebounder.
That said, he didn't anchor anything - Orlando had quality defenders in the line-up : Gordon is great, Isaac will be, Iwundu is terrific, Khem Birch also well. More of a team effort. And the one thing they were truly elite at was defensive rebounding. Hard do score second chance points on them.
If Vucevic improved defensively with Skiles/Vogel, he improved a lot offensively with Steve Clifford. The improvement on his 3pt shooting is obvious, but I was more impressed with his passing. He's become a very good passer/playmaker. Orlando had lots of defensive talent but very little offensive talent. If they weren't bottom of the league, it was mostly due to Vucevic playmaking.
That said, I'd be very skeptical of giving Vucevic a large long-term contract:
* Age, will play next season at 29
* Pretty sure he has peaked defensively. Very doubtful he'll keep up the hustling he showed last season in a contract year.
* Not sure he'll be able to sustain his 3pt shooting. And he was good but not exactly spectacular.
* Related, he's very reliant on shots from the top.
* While his offensive game gained a lot of variety last season, he isn't a 1st option. He's more a Horford type of player offensively -complementary playmaker/scorer- because he isn't that good at creating shots for himself in volume/efficiency.