Jimmer isn't tall enough to guard NBA 2-guards, so he's physically best suited to be in the game as a PG. Although he had adequate ball-handling skills for the NCAA, he's not an above-average ball-handler in the NBA. When defenses see him bringing the ball up the floor, they frequently pressure him because of this weakness, and it causes the half-court offense to stagnate and get a slow start in the shot clock. He also turns the ball over frequently when pressed with the ball. Between the turnovers and the poor execution in the half-court offense, he's replaced by PGs that don't have his offensive prowess but can handle the rock better than him.

IMO, developing some quickness and confidence handling the ball will have a great impact on his playing time than focusing on defense.