SIEM de Jong has undergone surgery after suffering a collapsed lung.
The foward, sidelined since early September, had been on the brink of a comeback from a long-term thigh injury.
De Jong – who previously suffered a collapsed lung at former club Ajax – will be out for eight weeks.
The 26-year-old said: “After four months of hard work getting back to full fitness, it is such bad luck to suffer another setback.
“We are all hopeful that the surgery I will have this week will ensure I don’t have any repeat of the condition in the future.
“It’s very sad for me personally, especially since I was almost back in contention and feeling great.
“I’m sorry for my team-mates, the club and our fans that I’m not able to help the team for a little while longer.
“I am determined to come back stronger as soon as possible. Thank you to everyone for your support.”