Atletico Madrid captain Koke is confident Joao Felix has the character to handle his €126 million (£115m/$140m) price tag but urged fans not to get on his back if he does have a couple of bad games.
Already a full Portugal international, Felix became the fourth most expensive player in history when he moved from Benfica to Atletico in July.
The teenager hopes "to be like" compatriot and former Liga star Cristiano Ronaldo, although Diego Simeone insists comparisons between the pair are shallow.
Strong inner belief does seem to be one shared trait, though, with midfielder Koke a fan of the forward's attitude.
"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."
The exciting youngster heads to the Wanda Metropolitano after an impressive season with the Portuguese giants and will be looking to help Atletico go one better this season by lifting the Liga title.
Koke, who has been at the club since he was six years old, enjoys the Portugese youngster's creativity and believes he has the ability to surprise the opposition.
"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.
Atletico fans might need patience with more than one player following the arrival of seven new signings during the close season.
Among them are full-backs Kieran Trippier and Renan Lodi, who face a steep learning curve as they come to grips with Simeone's disciplined defensive structure.
"That is no problem because the coach will instil it," Koke said when asked about the attack-minded pair's aptitude at the back.
"If you're good going forward, Cholo makes you good in defence."
Although there have been a host of arrivals at the club, there have also been plenty of departures, with Antoine Griezmann one of them after he opted to join title rivals Barcelona.
However, Koke believes they have the quality and desire in the squad regardless of having lost those that decided to depart.
"Those who want to be here have to be 100 per cent, if not raise your hand and ask to leave. Griezmann is gone, but Joao or [Hector] Herrera have arrived, people with enthusiasm that is what we need right now."