Willem II striker Mounir el Hamdaoui has suffered a potentially serious knee injury.
The former Tottenham man picked up the problem during Willem II's midweek cup victory over Flevo Boys.
He was replaced just 15 minutes into the game following a heavy challenge, and revealed later that he had heard a 'cracking' sound.
El Hamdaoui, who has been in good form so far this season, must now await the results of hospital tests.
Willem II have made a miserable start to their league campaign and may also have to do without defender Thomas Baelum for their next Eredivisie game against NAC Breda.
Baelum was red carded against Flevo Boys for a supposed elbow.