As far back as I can remember, only two players blew out their Achilles and returned at levels they played at beforehand: Dominique Wilkins and Kevin Durant. And that's going back 40-45 years or so.
I stated my evaluation process on this before the draft. If players are going to miss major time next year, up to being out all year, or are returning after being out a year or so, those teams trying to argue their health will be looked at less positively by me.
I think expecting Klay to return to his previous quality level of play after missing 2 whole seasons recuperating from 2 severe injuries is wishful thinking. Hayward broke his leg and took 1 and a half seasons of play before returning to his former self. That to me is a very realistic outcome for Klay.