Duke legend Jay Williams says he's 100% behind Mike Krzyzewski's new brand of justice ... saying the the Hall of Fame coach has to take "extreme measures" to right the Blue Devils' ship.
Coach K has been under some heat for banning Duke players from their own locker room, and forbidding them from wearing Duke gear until the team picks up it's poor play.
People are saying K's taking things too far ... but when we talked to the former Blue Devil and 2 time college player of the year .