The 19-year-old Spanish international came on in the second half on Thursday as he tried to work his way back after being ruled out for two months. However, he was reduced to tears after suffering the injury setback and had to limp off.
"Ansu Fati is very affected. It's a difficult situation. We've had a meeting with the family because of this new relapse," Xavi told a news conference ahead of Sunday's LaLiga game at Alaves.
"We want to recover him mentally, give him love because it is a difficult moment and we need him. It affects us all, although he is the main (one) affected. We want him to never be injured again," a worried Xavi added.
Fati faces another prolonged period on the sidelines after tests on Friday revealed he had aggravated an old leg injury.
"These are situations that you cannot control and we will draw up a recovery plan. On Monday we will decide what to do with Ansu Fati," Xavi said, explaining that more surgery could be an alternative.
Fati, who inherited Barca’s number 10 jersey from Lionel Messi, came through the youth system at the Catalan club but has been plagued by injuries. He had four operations to repair a left knee injury he suffered in November 2020.
Fati burst onto the scene for Barcelona at 16, when he became the second youngest player in LaLiga history.
He quickly established himself as one of the most exciting young talents in the world, becoming the youngest player to score in the Champions League and youngest to score for Spain.