His workload is too high.
POA defender at all times, handles the ball the most and plays a physical style of basketball that wears everyone down.
There was one possession where he defended high PNR 1v2, still managed to recover and close down Brunson, I think Bridges go the ball on the handoff, Castle switched on him and stayed close on his drive, contested a mid-range shot.
Basically played 20 seconds of defense by himself. And it happens many times over.
But it's a learning experience, as long as it doesn't cost us too many games.
Fox really needs the ball more, he's by far the safest option on offense and once he gets going he can take the game over.