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Xavi made 767 appearances for the Catalan giants before heading to Qatari club Al Sadd in 2015.
He played alongside Neymar for two years at the Nou Camp, winning the Champions League together in 2015.
And Xavi, 37, thinks the former Barca forward has the talent to lead Brazil to the World Cup final in Russia this summer.
"I think there will be a while after Messi and Cristiano [Ronaldo] when Neymar will be the reference point," the midfielder told El Pais.
"Especially as he is Brazilian; Brazil have every chance of making it to a World Cup final.
"The Neymar era will last three or four years, and then Mbappe's time will come. He has mad potential.
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“Neymar is like Messi: talent and physicality”
Xavi
"And he is still young; he's only 19. He is a monster."
Comparing the PSG pair to greats of the past, Xavi discussed how the best players team up technical talent with raw physical capabilities.
"I think that talent beats physical gifts," he continued.
"Neymar is like Messi: talent and physicality. I think that Mbappe has more physical gifts than talent.
"Players who have been truly gifted have both: Maradona, Pele, Ronaldo, Messi, Neymar.
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"Mbappe has talent too, but I see him as more of a [Thierry] Henry.
"Mbappe needs to improve numerous things in terms of his understanding of the game.
"Because, when he was a kid, he didn't need to think; he made the difference thanks to his power and pace.
"I would like to see Mbappe up against a defence like that of Atletico Madrid. The way I see things, right now Neymar is the better player."