Casagrande, who made 19 appearances for Brazil, has now questioned the 26-year-old, while dismissing comparisons to Barcelona great Lionel Messi and Madrid star Cristiano Ronaldo.
Brazil are one of the favourites for the World Cup this summer, but Casagrande is worried that Neymar's behaviour could prove troublesome at the tournament in Russia.
"It bothers me that most fans and media are still patting Neymar on the back," he told SporTV .
"He has already shown several inappropriate behaviours within a team. Against Real, he took a yellow in the first half and could have been sent off in the second.
"It would be disastrous if he acted like that at the World Cup. We are creating a monster, which some consider a genius.
"Neymar doesn't have the quality of Messi, [Diego] Maradona or Cristiano Ronaldo, who can win a match at any time."
The criticism of Neymar by Casagrande and others has not sat well with the player's father, who slammed his detractors after the Real Madrid defeat .
Neymar Sr. called the critics 'vultures' in a lengthy Instagram post, defending his son and backing him ahead the second leg at Parc des Princes on March 6.