Ajax and Netherlands defender Daley Blind has been diagnosed with a heart condition after suffering from dizziness during the Champions League game against Valencia on 10 December.
The ex-Manchester United player, 29, has missed the last two matches of the year and will not rejoin training in January as he continues his recovery.
Ajax said Blind had been "diagnosed with heart muscle inflammation" after extensive medical examination.
"I feel good at the moment," he said.
"I am trying to come back as soon as possible."
Blind has been fitted with a subcutaneous implantable cardioverter defibrillator, which sends electrical pulses to regulate abnormal heart rhythms, specifically those that can be dangerous and cause a cardiac arrest.