The 17 year-old will leave River after the Club World Cup this month.
Asked about his situation, Gallardo told ESPN: "It's natural, we train players for the world. Everything happens first, young players leave faster and faster, and I understand that these are the rules of the gamey.
"He was part of our project for next season. Now we have to reorganise, because there are players who, due to their profile, are difficult to replace.
"We knew that sooner or later he would leave, but the fans don't take this type of departure well. The market dictates the timing."
IGallardo has only one wish for him: "All I want is for him to play naturally, to be able to put aside everything that happens around him, even if it is very difficult. I do not talk to him about his future life in Madrid, nor about anything that comes from the outside.
"I just want him to do what he does best: play football."