Sometime it doesn't work like that. With that logic any half decent striker in our team would be scoring at least 20 goals because of Oscar, Mata, Hazard and we know that is not the case. Just like Barcelona having best players in the world in all the line yet doesn't win every single match. Mata might even struggle in their system and not flourish like our because our team is built to accmommodate him. Look at David Silva, much better player than Mata technically but fails to shine last season because City team wasn't built to accommodate him. Therefore even if Mata join MU, RVP will not score 20 goals extra or doesn't mean Mata will get 30-40 assists just because they have a world class striker in RVP.