In 2018, Joao Felix almost joined West Ham United from SL Benfica. He completed a $137.5 million agreement with UEFA Champions League challenger Atletico Madrid a year later, making him the fourth most expensive footballer ever.
Felix made his first team debut on the second day of the 2018–2019 season under then-manager Rui Vitoria.
Felix, 18, came on as a late replacement in a 2-0 win over Boavista and performed well enough to earn another call-up the following week against arch rival Sporting Lisbon.
Felix entered the Estádio Sport Lisboa as a 71st-minute substitute, but he became a Benfica hero by equalizing with four minutes left. He became the youngest Lisbon derby scorer with his spectacular header.