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Arjen Robben holds his thigh after injuring himself during a friendly international football match against Hungary on June 5, 2010. Robben is a doubt for the World Cup after injuring his left thigh in the Netherlands' 6-1 friendly win over Hungary today, Dutch coach Bert van Marwijk said. ((Toussaint Kluiters/AFP/Getty Images))

Netherlands coach Bert van Marwijk isn't holding out much hope that Arjen Robben will be fit in time to face Denmark in the team's World Cup opener.

Robben is nursing a hamstring injury that he picked up during a 6-1 win over Hungary in a friendly on Saturday, and was set to undergo further tests back home later Tuesday.

Van Marwijk, however, said he was all but certain the Bayern Munich player will not be ready to play against the Danes on Monday.

"It would be wrong to believe he would be ready to face Denmark," Van Marwijk said. "His injury is serious and I do not know when he can join us."

Robben was one of the main reasons why Bayern won the Bundesliga title and reached the Champions League final this past season with his ability to both score goals and create opportunities for others.

Van Marwijk has said he will not call in a replacement to the squad, and is still hoping the winger will be able to participate in later World Cup games. The Netherlands also face Japan and Cameroon in Group E.

Even without Robben, the Dutch coach still has a multitude of potent attacking options with a squad that includes Inter Milan playmaker Wesley Sneijder, Real Madrid midfielder Rafael van der Vaart, Arsenal striker Robin van Persie and Liverpool forward Dirk Kuyt.

Netherlands defender Khalid Boulahrouz also picked up a minor ankle injury in training Tuesday, but is expected to be fit against Denmark.