Neymar reportedly told PSG he wanted to quit in July, with both Barcelona and Real Madrid heavily linked with the Brazilian throughout the summer.
Having joined PSG for a world-record £200m in 2017, the 27-year-old has been the subject of talks with Barca this week.
Speaking to RMC Sport, Leonardo insists little progress has been made on agreeing to his return to the Camp Nou.
Neymar winning fitness battle to face Barcelona
With just over a fortnight remaining before the European transfer window closes on September 2, Neymar was omitted from PSG's squad for their opening Ligue 1 fixture against Nimes last weekend.
Several supporters held banners telling the player to "get lost" - and when asked about those reactions, Leonardo said: "Neymar has made mistakes.
I didn't know him before. Over time, I have got to know him. I honestly think he is a good boy with a very good heart. On the pitch, he is an extraordinary player.
There had been reports that the forward is no longer welcome as part of Thomas Tuchel's first-team group, but Leonardo added that this was wide of the mark.
PSG fans let Neymar know their feelings about him
Image credit: Getty Images
"It's wrong. He is not removed from the group," the former Brazil international said.
"He follows his personalised rehabilitation program. He's a Paris Saint-Germain player, he's still in Paris for three years, so do not forget. We must analyse everything, we must fix everything before he can play again."
Neymar has not played for PSG since May 11 and missed the Copa America with an ankle ligament injury.
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