Both youngsters are set to follow Sanchez out of Ajax this summer.
The Colombia international said, "It is difficult when you talk about a club like Barcelona. You change from an environment where you are indispensable and can play ninety minutes every game, to a place where you have to compete with the best players in the world.
"Because of the qualities they have, they can be calm with such a step, gain confidence and also be important. Ajax has given them a certain philosophy that identifies them now. The world is at their feet and they can compete with everyone. They have a great future."