I can't speak for anyone else but I use 6 as the baseline. Tau wasn't on for particularly long and, in my opinion, had no real effect one way or the other on the performance so he gets a 6.
Sanchez 7: didn't have a lot to do but what he did do he did with reassuring confidence. It's so nice seeing a keeper come off his line and comfortably pluck crosses out the air.
Burn 6: did ok, opne or two heart in mouth moments but dealt with what was in front of him effectively.
Dunk 8...