Let's discuss this, shouldn't sanchez goal ruled out as offside? It began with a lobbed pass to an offside arsenal player, then headed away by a chelsea player, sanchez picked it up and lobbed it again to the same offside arsenal player, but he never touched it, only for sanchez to pick up his own lobbed ball and scored the goal, besides the alleged handball.
But the important aspect is, there were 2 offsides prior to the goal, perhaps a strict interpretation of the rule is correct to allow the goal, but in the perspective of the defenders those 2 offsides confused and obstructed them from defending, I think it's not fair to the defenders.