Spo holds players to standards and challenges them every night. He has the unique ability to take a player who has struggled in the past and build a system to fit what they can do best. Spo has made a living doing this in Miami, and Mitchell is the latest player to see the dividends of trusting (and buying into) the Heat's coaching staff.
That last point may be the understatement of the century. Mitchell is among the NBA's most suffocating on-ball defenders. If he is suddenly going to be an above-average shooter, on real volume, he's not simply a net-positive player. He's one of the Heat's most valuable players, on one of the league's best contracts. Period.