Uruguay defender and captain Diego Lugano said Neymar was "very apt at pretending to be fouled" and warned that this should be watched closely.
Lugano's comments drew an angry response from the Brazilian Football Confederation (CBF), who issued an official statement just a few hours before the match.
"What Lugano is trying to do when he talks about Neymar is pressure the referee into not punishing the tough tackles that he will doubtlessly make on the Brazilian player," the CBF said.
"When he questions Neymar's behaviour on the field, Lugano makes the huge mistake of a purported analyst by calling into question something that no football fan would dare to doubt, the talent of Brazil's No. 10."
The CBF also pointed out that Neymar had scored in each of Brazil's three games thus far and was elected as 'Man of the Match' in all of those games by fans who voted in an online poll.
However, the striker - who recently signed a five-year deal with Barcelona - has a reputation for diving in his homeland and he went down easily to win a free-kick, which he curled perfectly into the top corner in Saturday's match against Italy.
Brazil have a 100 percent record in the tournament so far, but are expected to face their toughest test against their old foes Uruguay.
In their three group games, manager Oscar Tabarez's side beat Nigeria and Tahiti but stumbled against World Cup winners Spain.
