Former Brazil international Walter Casagrande slammed Paris Saint-Germain star Neymar, saying a "monster" was being created.
Neymar was unable to inspire PSG on Wednesday as the Ligue 1 giants suffered a 3-1 loss at Real Madrid in the first leg of their last-16 Champions League tie.
Casagrande, who made 19 appearances for Brazil, slammed the 26-year-old, while dismissing comparisons to Barcelona great Lionel Messi and Madrid star Cristiano Ronaldo.
"It bothers me that most fans and media are still tapping 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."
Meanwhile, Neymar's father hit back at critics of his son on Instagram.
Posted along with an image of Neymar, his dad wrote: "In a 'war' there are always the ones who feed on victories and those who, like vultures, feed on carrion of the defeated. They do nothing, make nothing but living on the shine or, more often, on their 'preys' most difficult moments.
"We know a lot of people on the football world that have this 'vulture behaviour', without much of their own glow, always on the shadows of the most talented, to vent their own frustrations. They enjoy defeats, or a lost BATTLE, to lurk around, waiting for the war to be lost to feed their own egos as vultures feed on carrion.
"They failed to do so on the Rio Games but stood there, waiting for their first chance to bring their bad omen. But remember: we lost a battle, not the war. My son has always been 'waging' this war, facing the good combats, dodging vultures and coming back stronger each time!! Mostly, he always respected everyone, even the vultures...
"We lost a battle, as for the war we'll see, it will go on as long as he's on a football pitch. And be sure of this, he'll be reborn as a phoenix, prepared for as many combats there will be ahead! As for you, vulture, you'll be left starving. And there will be nothing left but to swallow your words, as rotten as carrion."
