http://www.nba.com/article/2017/10/0...h-transition#/
THE CONTEXT
Good defense starts in transition, because league-wide effective field goal percentage drops from 60 percent in the first six seconds of the shot clock to 50 percent thereafter. If you can get back, prevent those early shots, and make your opponent play in the half court, you're in decent shape defensively.

After three rough years under Byron Scott, the Lakers brought in the guy who had coached the league's No. 2 defense over the first 43 games the season before. But Luke Walton couldn't make an impact on that end of the floor, as his new team ranked last in defensive efficiency for the second straight season.

Bad defense starts in transition, too. Last season, only two teams allowed their opponents to take a greater percentage of their shots in the first six seconds of the shot clock than the Lakers did. And no team allowed their opponents to shoot better in the first six seconds. Opponent transition possessions were both frequent and efficient.