I think a realistic and conservative expectation would be top-30. I think he will be in contention for a while but consistently lose time to the top riders. On the tricky stages he won't have good placing and lose time, then on the first real mountain stage he will lose a fair amount and in the third week have a complete off day. In the end it will be enough for somewhere between 25th and 30th, which IMO would be pretty good, nothing to write home about of course, but a good basis for the Vuelta and next year's Tour and proof that he is able to race at the highest level again.
I am hoping that his continuous time loss will enable him to go for Mont Ventoux or Alpe d'Huez glory!