Captain Robin van Persie may miss Holland's World Cup semi-final against Argentina as he is struggling with an upset stomach.
Van Persie has been instrumental in Holland's run to the last four of the tournament, but he had to train separately from his team-mates on Tuesday after complaining of a stomach problem.
Coach Louis van Gaal confirmed on the eve of the game in Sao Paulo that his star striker, who has scored three goals in Brazil, is a serious doubt for the last-four clash.
"He has a stomach problem, an intestinal problem. I don't know (if he will play)," Van Gaal told a press conference.
"I will decide (on Wednesday).
"Van Persie is our captain so he is very important to us.
"In principle my captain always plays, but he has to be fit."
There was some good news for the Holland coach on Tuesday as injury doubts Ron Vlaar and Leroy Fer took part in training.
In an interesting development, midfielder Nigel de Jong was also involved even though he had been expected to miss the rest of the World Cup after suffering a groin injury in the group stage win over Mexico.
"If his reaction is good and he can play, then the miracle can come true," Van Gaal said.
But even if De Jong makes a shock return to the XI for the Argentina match, it will mean nothing if Van Persie is ruled out.
Holland have relied heavily on the Manchester United striker, and fellow star Arjen Robben, in Brazil.
Both players scored in the penalty shoot out win over Costa Rica which sent the Dutch through to their second successive World Cup semi-final.
That match was a draining affair as Holland battered the Costa Rica goal, but they could not beat Keylor Navas inside 120 minutes.
Van Gaal thinks his players will have recovered their fitness by the time they face Alejandro Sabella's team.
"In general I give the players two days to recover, so if you have one day less it's an issue, a problem," Van Gaal said. "But a top athlete can perform so my players will be in shape."
Van Gaal's decision to bring on Tim Krul in the 120th minute of the quarter-final was hailed as a master stroke.
Krul saved two penalties after replacing Jasper Cillessen, but the Newcastle stopper will not start the semi-final.
"No. I ruled that out straight away," said Van Gaal when asked if he would start with Krul.
"Jasper is doing a wonderful job, it was just that stopping a penalty is something that the others (Krul and third choice Michel Vorm) are better at."
Although Argentina are yet to hit peak form in Brazil, they are the bookmakers' favourites for the match at the Arena Corinthians.
Van Gaal believes there is nothing between the two sides though.
"I don't think there is a favourite," the Manchester United manager in waiting said.
"The countries are at the same level. It's a 50-50 match and we have to be a bit lucky too."
Key to Holland's chances of making the final will be how they deal with the threat posed by Lionel Messi, who has finally transferred his domestic form with Barcelona onto the international stage.
"He has been voted the world's best player before and you don't get that for nothing," Van Gaal added. "He has always found it hard to show his form at international level.
"He wants to do it at this tournament and we want to stop him.
"That will be a challenge."