For nearly the entirety of his 19-year career in the NBA, Jason Kidd has been praised as a coach on the floor, an extension of the coaching staff, the smartest player with the quickest mind, reacting instantaneously — maybe quicker — to the whirlwind of activity on the court.

But just a week after Kidd decided it was time to retire in the midst of a three-year deal with the Knicks, he is headed toward an interview this week for the Nets’ coaching job. And it is worth thinking long and hard about the transition from coach on the floor to head coach.

There is no doubt that Kidd is a basketball savant, but that is with the ball in his hands and his Hall of Fame skills running the show. Is it an innate knowledge or something he can teach to a player who doesn’t possess his physical skills and a basketball mind that processes plays as they happen, and sees the next move before most players have scanned the current one?

Kidd wouldn’t be the first head coach never to have spent a day as an assistant, but it would be such a quick turnaround from player to coach that it almost seems like a throwback to the player-coach days of Bill Russell or Dave DeBusschere. The toughest part of that job is finding the delicate line between player and coach, between employee and friend.

Kidd should know the line well, having been the star of nearly every team he has been a part of and an extension of the coach — but not the coach. But on the bench, the ball isn’t in his hands. Instead, the head coach inherits just every other problem, blame and sleepless hours. Kidd will be stuck to the sidelines while he watches lesser talents work to mimic things that came so easy to him as a player. It would be like trying to teach your child to drive, and by the time you are a mile from home both teacher and pupil are at each other’s throats.

The other difference is the pupil will be a highly paid, coddled player. In the case of the Nets, the star pupil and biggest problem at times is Deron Williams — who drove basketball lifer Jerry Sloan from the game, who underachieved for half a season as Avery Johnson lost his job and who sat quietly as P.J. Carlesimo departed without an endorsement from the star.