Fati made his debut at 16 for Sunday's 5-2 defeat of Real Betis.
Valdes commented: “If I have to define something what the day meant to him, the number with which he debuts says it all: it is a '31'. For those of us at home, debuting at Camp Nou at 16 years and with a number '31' tells you that he is an elite player, not anyone with that number does that.
"There are many numbers below that.
"I am grateful to (Ernesto) Valverde for giving him those minutes, and well ... It is a pity that tomorrow we cannot have him at the Nou Estadi because in the end it is also representative to have such a figure, the pearl in this case of the La Masia in this game that tomorrow we will live. Out of respect for Johan too."
Valdes was speaking before his team's clash with Juventus to open the Estadi Johan Cruyff.