Young Ajax striker Kolbeinn Sigthorsson is expected to be out until the Eredivisie winter break with an ankle injury.
The Iceland international underwent a scan on his damaged ankle, suffered during last weekend's 1-0 defeat to FC Groningen, which revealed a stress fracture.
The Amsterdam club confirmed the news on their official website on Wednesday morning.
Sigthorsson, a summer arrival from title rivals AZ Alkmaar, had featured in all eight of Ajax's opening league games, scoring five goals.
Meanwhile, Belgian defender Toby Alderweireld has returned to his club with a back problem having reported for international duty at the start of the week.