The 19-year-old signed for Atleti from Benfica back in July for €126 million (£113 million):
Felix will get his first taste of competitive action at Atleti when they kick off their 2019-20 La Liga campaign against Getafe on Sunday at Wanda Metropolitano.
Oblak, who has established himself as one of the best goalkeepers in the world at Atleti, is confident Felix can live up to his enormous potential, per Football Espana:
"We are still in pre-season but it is clear that he has huge talent. With talent like that he can grow into being a magnificent player, I am sure that this is the right place for him. He is going to progress a lot under [manager] Diego Simeone and he is going to learn a lot here. There is no doubt that he is a great talent. If he continues on the same path as he started, if he trains and keeps playing at the level he has shown then he will be a world class player, no doubt."
Felix has played only one season of senior football.
He debuted for Benfica last August and went on to play a key role as they won the Primeira Liga, netting 15 goals and providing seven assists.
Playing in La Liga will be a big step for the Portuguese teenager, but Atleti are clearly confident in his ability, otherwise they would not have shelled out a club-record fee to sign him.
He has the ability to play on either flank, but he will likely take up a central role in the new season following Antoine Griezmann's departure to Barcelona.
The Frenchman was talismanic for Simeone's side during his five seasons at the club, and Felix will need to hit the ground running in La Liga if he is to make up for Griezmann's departure.
Oblak clearly has few doubts about the youngster's ability, and the goalkeeper's acclaim will likely give Felix's confidence a big boost ahead of the new term.