Grau insists the former Ajax defender chose to go for the money.
“We made him an offer, but he preferred to go to Juve, where Italian taxation allows him to earn a higher net salary," said Grau.
Barca also tried for PSG star Neymar.
"We made a very big effort for him," Grau said.
“The club did everything possible with two offers, one with and one without players in exchange but still sustainable.
“The feeling, however, is that PSG never really opened up to a sale."