I don’t think his ceiling is very high at this point. Barca sold him for peanuts to Benfica.
I also think his small stature (5’7 and not very physical) would be a problem in the Premier League. Being that small may be OK as a fullback when you are Jordi Alba or Dani Alves and you play for an incredible team that doesn’t defend a lot. But its not ideal if you are playing in the Premier League against opponents that live and die by the crossing game and you are often asked to win headers on crosses to the back post.