Unreal.
Pierce is 35 years old. Check the stats. 35 year olds MJ, Larry Bird, Scottie Pippen, Julius Erving, Jerry West, Alex English, and a host of other great wing players all played big minutes and very well at 35 years old.
Pierce is in some of the best shape of his life and still playing an all around game that is far better than Jeff Green's game. You don't sit a better player simply because he might be older than another or because you have a man crush on the bench player.
That's just bad basketball coaching.