People always seem to talk about how yay has either incredible aim, or how he shows insane game sense in certain scenarios, but imo one of the biggest strengths of yay is that he does close to no mistakes. When have you ever seen that guy overpeek? When he repeaks it is usually a risk that is worthwhile taking. Now, this could be the case because yay is to passive, but his impact and his kills speak for it self. This paired with his consistency makes him the dream of a coach, since you will always get a certain value out of him, no matter his day to day form and it also ensures economical stability since the op is really expensive.
This is also especially incredible if you consider the fact that he HAS to get very high value as an oper, since a oper who doesnt kill is wasted money. If a rifler overpeeks it is far less devastating than if a oper overpeeks.