The teenager is yet to officially move to England due to his age, but the 17-year-old has enjoyed an excellent start to his professional career with Fluminense.
Watford moved fast to secure the teenager's future when paying an initial £2million in September - before he had made his senior debut.
It appears they got more of a bargain than many anticipated with Pedro blasting in the goals back in Brazil, registering three times in the league and a further three in the Copa Sudamericana - South America's Europa League equivalent.
Such form has convinced Barcelona general manager Pep Segura that he is a talent worth pursuing, according to Sport.
And their hastiness is being increased by United and Liverpool pondering similar moves.