Barca president Josep Maria Bartomeu is exploring how he can buy back the Brazilian, who has resisted new contract talks with PSG to stay clear for a Nou Camp return.
Eto'o says signing Neymar would be a great coup for the Catalans.
He said, "In terms of football, there is no doubt that he is one of the best 3 or 5 in the world, he can make a difference.
"I played with him and he has a positive character. A transfer for Neymar would be beneficial for Barça, it would be an extraordinary signing to make a difference."
Sassuolo defender Marlon, also formerly of Barca, agrees.
He also said, "Barça is a stage for great players. This is what Neymar is and he would do well to go back."