play down a position rather than play up a position.  Zac isn't best in the post, despite his length.  He is better on the wing.  Better if he can play down a position rather than up a position.  Same for Yoeli.  Yoeli is a dominant PF and against most he is even good enough to hold his own in the 5 spot.  But, Payton allows Yoeli to play where he is most dominant, at PF.  Let TJ play some 2 guard, but also let him play more at PF.  I like McKay.  What hustle and he learned to play D at Weber St.  I like his effort on D.  He plays his role.  But, he is less dynamic than Payton. 

Play Payton more and allow everyone to shift down a position rather than playing McKay and making everyone play up a position.

I don't have any inside info, but it appears that Mika left because he wanted to play PF rather than almost exclusively at center.  Rose could have rotated Corbin in the middle last year and let Mika play PF while Yoeli was catching his breath for a few minutes. 

Dave Rose regularly plays guys up a position rather than down a position.  He regularly prefers wings over post players and Zac is an example.