That's the weird thing to me. It's not like he is buried on the bench...he's become the first big off the bench after Poeltl, which is exactly where he should be. His minutes are actually increasing as the season goes on and he learns the system, and he's been helping to produce wins.
I understand being upset about Chicago trading him and having to move his life and going from a team that is currently successful (Chicago) to the Spurs who are rebuilding...but that's the business.
Maybe this is all just smoke, and more playing time will placate him. If not, shut up and do your damn job, you are still getting paid and getting played.