I think peoples expectations of him are sky high, he is going to be used mostly as a later sub imo, someone off of the bench to slow it down and use his experience when winning and someone who can come on and make something happen if losing. I don’t see him as a regular starter at all.
I think you are going to be surprised, this guy will be a starter from day one
Thiago Silva is 37, played 48 games for Chelsea this season including 32 in PL, Modric as everyone mentioned is 36, Ronaldo 37, Vardy 35 (as a pace dependent striker), Cavani 35. Modern players have no problem playing longer.
PL & CL games will go to Perisic, domestic cups and perhaps some lesser games or mid-week games will go to Sessegnon.