The Dutch winger admitted that he was guilty of simulation in his country's win over Mexico, and the Tico's coach is "very worried" about a repeat performance at Arena Fonte Nova.
The Dutch winger caused controversy by admitting that he had been guilty of simulation in his country's last-16 win against Mexico, although he denied having gone to ground of his own accord for the late penalty that decided the game.
Pinto, therefore, is extremely concerned by the prospect of Robben's alleged theatrics having an influence on the outcome of his side's meeting with Louis van Gaal's team at Arena Fonte Nova.
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"This is one of the most important questions in the World Cup: diving," he told reporters in Salvador on Friday. "We're really worried about it. I would like the referee and FIFA to watch Robben closely. He's one of the three or four best players in the world. I have a website and I analyzed him as a player on it; he's amazing.
"But we have to say that there have been mistakes in this World Cup and we're really worried about Robben's diving, which he admitted. He admitted it!" Pinto continued. "So I hope that the officials are very careful tomorrow [Saturday]. I urge them to watch out.
"We hope that there are no mistakes so, please, I would like to ask Fifa and the officials to watch out and be careful. This is very important and could have a big impact on the result."
Pinto was asked if he would like to see Robben immediately booked if he is deemed guilty of simulation early on in the game, so as to act as a deterrent to any other diving.
"That would be the most logical conclusion," he said. "Maybe he would have to leave the field for diving twice. That could happen.
"But you know what? I want to trust the referee, so let's just hope nothing happens."
Uzbekistan's Ravshan Irmatov will be the man in the middle of Saturday's last-eight encounter in Salvador.