Gavi opened the scoring in the 33rd minute, before getting the assist for Robert Lewandowski’s 45th minute goal to make it 2-0.
Pedri added another to open up a three-goal buffer, before Karim Benzema’s late consolation in Riyadh.
“I’m left speechless,” Xavi told Marca. “He’s pure passion, pure soul.
“It leaves a bad taste in my mouth when he doesn’t play. He’s contagious for the team and he’s only 18 years old.
“The heart he puts into it is incredible. Gavi is a kid who excites us all. He puts in soul and character and infects the rest of the team with it.
“He is an innate leader and it comes from within. The rage that comes out of him is spectacular. I never tire of praising him. This boy has no ceiling.”
Barca president Joan Laporta was delighted with the Blaugrana, who are also atop La Liga, while he threw his support behind boss Xavi.
“He has knowledge, personality, a style of playing football that Barca shows and we express ourselves in this way,” Laporta said.
“He is one of the architects of this genuine way of playing football.”