The two forwards have drawn comparisons for their explosion onto the scene in recent years, impressing under pressure despite their inexperience on such a big stage.
Sunday's Clasico will see them come head to head with Vinicius in the best form of his career and Ansu returning after a year on the sidelines with a knee injury.
"Vinicius is quicker, more electric, he's more of a pure winger," Pique said of the comparison between the two young stars.
"Ansu scores more and can play as a striker. I'd say Ansu scores more and that the other one is more electric, and in one-on-ones, he's one of the best in the world."
Fati signed a new contract to commit his future to Barcelona until 2027 this week and will undoubtedly play an important role in the fixture on Sunday.
"Barcelona need players like that, goalscorers," Pique added on the teenager.
"The people need it, and even more when the most important player in our history has left, but we have to be realistic with him.
"He's 19 years old and here the one who has to win games is the team, he helps with goals."
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