With Lionel Messi and Cristiano Ronaldo opting to leave Europe for the twilight of their illustrious careers, football fans are eager to discover which players will pick up the baton as the best players on the planet. A rivalry between Kylian Mbappe and Erling Haaland has been talked about as the next big battle for supremacy on the pitch, but we're looking for the next batch of potential gems who are even younger at 21 or under.: