I wonder how known he is to the world outside Barcelona and Spain.
It might take a few years before he'll be considered one of the best midfielders in the world even if he'll reach that point much earlier.
Since you asked "outside Barcelona and Spain":
- he is known very well in Brazil, a country of 200 million people. He became last year a starter in the Seleção, so he will be known around the world ALSO because of that.
- he is very well known in South America because of Libertadores. He was the best player in the final of 2017. Commentators from other south american countries were praising him almost the entire Libertadores 2017 (which was his first).
- being known in Argentina and Brazil will mean a large number of other S.American players in Europe will have heard about him, as they follow their ex-clubs, have families that follow local clubs and leagues, agents who also are agents of players still in S.America, etc.