This article on Coach Nurse doesn't answer that question, but it gives some hints.
He's in charge of putting together the film clips the player watch as well as working independently with players (PPat in this example). And the article suggests he puts together video at the end of the season to assist in player development.
We have heard endlessly about how Casey was responsible for the Mav's defensive prowess in their last championship season. I have been a great advocate of spending team money on personnel other than players, since there are no cap implications. A team that highers the best assistant coaches, strength and conditioning coaches, trainers, video people, stats guys, sports psychologists or whatever just has to have an advantage, all things being equal, over another team with similar playing talent. And it should prove out over the longer term. I think it makes an impression on players when making decisions about whether to accept FA offers as well. A team with a reputation as very professional and obviously dedicated to winning would have to be considered as a better destination than a team that looked like it was staffed with the Barnum and Bailey clown department.