The 18-year-old is a product of the Stars of Africa Academy in Johannesburg and is already an Under-20 international for South Africa, having helped the team lift the Under-20 Africa Cup of Nations in Egypt last year.
Stars of Africa Academy owner Farouk Khan has long had a connection to Brazil, and the aim of getting Modiba over to South America is to help him get used to living away from home, as his enormous potential has earmarked him for a career abroad.
Khan shared a highlights reel of the player from a recent game in which he appeared to earn, and score, two penalties. He officially signed for the club in January after his 18th birthday, having been in Brazil for an assessment last year.
He is a player not dissimilar in style to Cape Town City playmaker Emile Witbooi, another who is seen as a future Bafana Bafana international.
Modiba is, for the moment, the only South African at a Brazilian Serie A club, though others have been there before.
Mark Williams played for Corinthians in 1996 and Tyroane Sandows was in the Grêmio first team in 2016/17.
Modiba is not the first player Khan has sent to Fluminense either. Luther Singh trained with the team and with Vasco da Gama at the age of 16, before heading to Sweden, where his senior career was launched.