Costa Rica coach Jorge Luis Pinto is "really worried about" Arjen Robben's diving and pleaded with officials to be vigilant in their World Cup quarter-final against Holland.
Los Ticos have been the surprise package in Brazil, overcoming Uruguay and Italy before holding England to a goalless draw as they won Group D.
That dream run continued in Recife on Sunday as they rode their luck against Greece to win a tense clash on penalties, setting-up a quarter-final clash against Holland.
The Oranje produced a remarkable late comeback to deny Mexico in their last-16 clash, after which Robben made headlines by admitting he did dive earlier in the match .
The winger was insistent he had not taken a tumble for the penalty from which Klaas-Jan Huntelaar struck the winner, but his dive has concerned Costa Rica coach Pinto.
"This is one of the most important questions I have been asked in this World Cup," Pinto said.
"Diving. This is something that makes us worry a lot. We're really worried about that.
"I would like to ask FIFA and the referees to watch Robben closely. We're really worried about his diving.
"He has admitted to doing it," Pinto added. "I hope the referee watches him very closely tomorrow.
"I would like FIFA and the referee to watch out because it is very important and can have a huge influence on the result."
Ravshan Irmatov of Uzbekistan will be taking charge of the match and Pinto hopes he is brave enough to book him should he dive.
"That may be the most logical solution," he said. "Maybe he would have to leave the field because he gets two yellow cards for diving.
"Why not? That could happen. I want to trust the referees. Let's see what happens."
Robben will play a key role for the Dutch in Salvador, where captain Bryan Ruiz hopes Costa Rica can extend their record-breaking run.
"Maybe in a few months this will all sink in, but for right now we're just trying to enjoy what we're living," he said. "We have nothing to lose.
"We've come so far and done so much, but we want more. We want to continue on and see how far this can go."
For Ruiz, this is a particularly special match considering he is playing against the country where he has spent so much of his professional career.
The 28-year-old made his name with Twente, playing there between 2009 and his big-money move to Fulham in 2011.
Ruiz returned to Holland earlier this year after falling out of favour at Craven Cottage, impressing during a loan spell at PSV Eindhoven.
"It's nice to play against a team like Holland, but it's difficult too," he told www.fifa.com.
"I have so many friends in the Netherlands. The place was my home for years and I care about its people. But for us it is a dream to play in the quarter-finals.
"We know we're doing something so big for the people back home, but maybe we don't realise the extent of how big just yet."