Lamine Yamal, a 15-year-old from Barcelona's La Masia academy, is in the matchday squad.
He could become the youngest Barcelona player of all time.
Yamal is the youngest ever player to be part of a Barcelona squad for an official game.
Xavi has praised his talent and personality.
Yamal was born on 13 July 2007 and has been at Barca since he was five.
He will be 15 years and 285 days old if he makes an appearance on Sunday.
Barcelona are eight points clear of Real Madrid at the top of La Liga with a game in hand.
Xavi has been able to include Pedri and Frenkie de Jong in the squad after injury.
Xavi said Yamal is an innate talent and difficult to compare to other players.
Barcelona has played out goalless draws in their last two matches against Getafe and Girona.