Ajax striker Kolbeinn Sigthorsson will be sidelined until the winter break in January, the Amsterdam based club announced on Wednesday. His ankle injury is more serious than expected. Medical examination showed a so-called fatigue fracture in his right ankle. Last Sunday in the league match against FC Groningen Sigthorsson left the field injured after 19 minutes. The 21-year-old Icelandic international will miss the remaining league matches this year and also the last four matches in Group D of the Champions League. Sigthorsson, who arrived from AZ Alkmaar this summer, scored five times in eight league games this season. Belgian defender Toby Alderweireld returned to Ajax with an ankle injury on Tuesday. The Belgian international suffered the injury while training with his national team. The ankle should heal with rest.