Here is my observation on this, if anyone cares...
The times when Layman actually started or played significant minutes this year he was mostly used defensively the same way Harkless was, not Aminu. For example, the 2nd half of the one game against Denver that he started he was tasked with guarding Jamal Murray. In other words we had Layman on their best perimeter player. Harkless struggled all series getting through picks and staying in front of Murray yet Layman can't defend because Murray went by him too a couple times?
This is why the evolution of Dame's defense is fairly important. For the last couple years it's usually been Harkless who guards the other team's best perimeter offensive player. Asking Layman to come in and do the exact same thing every time and expecting him to lock guys down is a little unrealistic. Much like Simons, Layman needs to take his lumps learning how to defend at that level. I think he has the athleticism to be a good defender if he does get the minutes to learn from it.
I may be wrong but I think it would be a huge mistake to let Layman walk this summer. Since our starters don't seem like they'll ever play at a fast pace I wish the bench would be designed to come in and just run teams to death. Guys like Simons, Skal, Collins, and Layman would excel if that was the case.