They could all play a role in the front 3 I agree, but if we got to Feb / March and either Jesus or Aguero got injured then the other one would have to play centrally every game, Sane, Sterling, Roberts and the 2 Silvas couldn't fill in centrally without a big drop off at the crucial hopefully busiest part of the Season Sanchez could. Plus if Bernardo Silva is being relied on to cover the front 3 it leaves us short for resting Silva as well and we saw the drop off this season when he wasn't available.