Felix became the fourth most expensive signing in football history when he completed a £116m move from Benfica to the Rojiblancos in the off-season.
The 19-year-old has huge pressure on his shoulders to justify his enormous price tag and he has also been handed the number 7 jersey previously worn by Antoine Griezmann, who has left to join Spanish champions Barcelona.
Felix’s potential has already led comparisons with his countryman and five-time Ballon d’or winner, Cristiano Ronaldo, but Koke, who recently replaced the departed Diego Godin as the new Atletico Madrid captain is urging fans to be patient with the Portuguese.
"He has a lot of personality," Koke told El Pais.
"It's not easy to be 19 and have the pressure of what has been paid for him.
"You have to give him some time. If he plays two bad games, you can't kill him."
"He enjoys playing football. He has a lot of quality, but what I like most is the mischief [he creates], the dribbling. He likes to have the ball; he is not afraid to ask for it," he added.
Felix, who was part of the Portugal squad that recently won the inaugural UEFA Nations League, has already shown glimpses of his undoubted talent, scoring once and setting up two more as Atletico Madrid defeated Real Madrid 7-3 in the International Champions Cup.