Dereck Lively fell behind at Duke because of his injury and it took awhile for him to round into form. Once he did, people got it: he is 7-1, he’s highly agile and he has great defensive instincts.
That’s what we saw at Duke anyway because that’s what the coaches needed him to do and Lively, being highly coachable, willingly filled that role because it helped his team to accomplish more (this is an underrated trait of his and it will help him immensely in the future).
In the NBA, people are starting to realize that the high school version of Lively, where he displayed a fluid offensive game out to the three point line, is also making an impression.