“The Spanish international has a bruise on his right hip from training on Friday,” Barca wrote in a statement, without confirming how long they expect the 17-year-old to be out for.
Fati is unlikely though to feature in Barca’s friendly against Gimnastic Tarragaona on Saturday.
They then have two more friendlies against Elche and Girona before beginning the season against Villarreal at the end of the month.
Fati is one of the most exciting prospects for the new campaign in LaLiga.
He scored on his first start for Spain on Sunday against Ukraine to become the country’s youngest ever scorer at the age of 17 and 311 days.