Brett Brown has the technical tools to be an NBA head-coach, he's a Popovich disciple after all.
IMO his biggest mistake, always has been, was to pander to the players ex. Allow Joel Embiid have control of the offense ........... Embiid is so talented, yet he does not have sweet spots where he'll ask for the ball.
They just gave the ball to Embiid, wherever Embiid likes to get the ball, usually jack-up some mid-range or long-ball.
Many NBA columnists have quoted other teams coaching staff, saying that Embiid taking jumpers is a gift from heaven.
I agree that Elton Brand made some big mistakes e.g. over-paying Harris, trading Butler, letting Reddick walk, etc......... I was actually surprised when he was made GM some years ago.
Some NBA teams (SPURS, HEAT, RAPTORS, CELTICS, etc) have long shown that GM duties require analytics, cap management, player development, etc, something not usually equated with most ex-players ......... Sam Presti, Ujiri, Buford, Elisburg, etc
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Right off the bat, Mark Jackson should be a good head-coach for the 76ers ........... a players coach like Brett Brown, yet he commands respect.