TBF Robertson's legs were very clearly shot last season - some rather average teams/players made him look incredibly ordinary.
I hate to say that about someone who's been legendary for so many years, but the reality is it happens to every player eventually.
Interesting you saw it that way. Just to point out he got voted top 8 MVP in the league along with HBU player of the year last season. He has also just completed a full Napier winter season being a key part of them winning the league. Yes he is a bit older now and in the twilight of his career, but he surely still has a lot to offer on the pitch, on the training pitch and also off the pitch. Always conducts himself professionally with gym work and eating habits. So there is no way his body won't be ready if he still feels it is.
It's a completely political based decision and nothing towards his ability as a player.