Mendes, who represents Yamal through his Gestifute agency, framed the challenge in direct terms when speaking publicly about his young client's setback.
"Cristiano is the best player in the history of football and also an irreproachable example off the field. That is the model we must pass on to children," he said.
"I always ask them if they want to be like Cristiano or Messi off the field — or like others."
Yamal suffered a biceps femoris tear in his left leg during Barcelona's win over Celta Vigo on Wednesday and will miss the remainder of the domestic season. He also posted a message on Instagram expressing his devastation at the timing.
"This injury keeps me off the field at the moment I most wanted to be there, and it hurts more than I can explain."
His World Cup place with Spain is not considered to be at risk. Spain's opening fixture against Cape Verde is not until 15 June, giving him enough time to complete his recovery if there are no setbacks.
Mendes had previously described Yamal as "the player everyone is talking about worldwide" and said the responsibility that comes with that status requires singular focus. "Having everyone watching you is also a great responsibility and a lot of pressure. He's handling it very well."