JOHANNESBURG, June 8 (Xinhua) -- Netherlands coach Bert van Marwijk is not counting on Arjen Robben to play its World Cup opener against Denmark.

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

Van Marwijk said: "His injury is serious and I do not know when he can join us."

Arjen Robben of the Netherlands is pictured prior to their soccer friendly against Hungary ahead of the World Cup 2010 in Amsterdam June 5, 2010.

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.

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

The Netherlands also face Japan and Cameroon in Group E.