Joao Felix's value could be "doubled or tripled" within a year, according to his new Atletico Madrid team-mate Felipe Monteiro.
Both players have moved to the Wanda Metropolitano Stadium from Portugal this summer.
Centre-back Felipe signed from Porto for €20 million (£18 million), while Atleti smashed their transfer record to snap up Felix from Benfica for €126 million (£113 million).
B/R FootballOne of the most expensive signings ever. 19 years old. https://t.co/k3Jmw6NyyB
Given the 19-year-old has only played one season of senior football in his career, the Madrid outfit have taken a risk paying such a huge fee.