Florian Lejeune is facing a lengthy lay-off after suffering a serious knee injury.
Rafa Benitez has revealed that the Newcastle United defender has damaged his cruciate ligament.
Lejeune, signed from Eibar a year ago, will undergo surgery.
Speaking after last night's goalless draw against Porto at the Estadio do Dragao, Benitez said: "I think it's a cruciate ligament.
"He will need an operation. We need to decide exactly when, but I think we will lose him for a while."
Lejeune played in Newcastle's first pre-season game against St Patrick's Athletic.
However, the 27-year-old sat out Tuesday night's game against Hull City and didn't travel to Portugal with his team-mates.