THE HAGUE, May 27 (Xinhua) -- On the last day of the training camp of the Dutch national team in Portugal, Rafael van der Vaart suffered a calf injury, Dutch media report on Tuesday.

On Monday Van der Vaart had already missed a training due to a mild fever. The 31-year-old Hamburger SV player will undergo a further medical examination later on Tuesday. He will leave Portugal with the Dutch team this afternoon.

Van der Vaart's participation at the World Cup is in jeopardy. He seemed battling with Feyenoord midfielder Georginio Wijnaldum for the second playmaker spot in the squad after Wesley Sneijder.

Van der Vaart already struggled with his form and fitness in the second half of the season. He is not the only injury case in the Dutch selection. Right back Paul Verhaegh suffers from an ankle injury, while the other right back Daryl Janmaat just recovered from the ankle injury he sustained in the friendly against Ecuador on May 17 (1-1).

Dutch head coach Louis van Gaal will announce his 23-man World Cup on Saturday ahead of the friendly against Ghana in Rotterdam. The FIFA deadline for naming squads is June 2. The preliminary squad of Van Gaal consisted of 30 players, of which 26 were in Portugal and four were playing for the Dutch U21 team. So seven players still have to be dropped.