Newcastle United manager Rafael Benitez has revealed that Florian Lejeune has damaged his cruciate ligament and faces a lengthy spell on the sidelines.
The 27-year-old defender played in Newcastle's first pre-season game against St Patrick's Athletic but was absent for Tuesday's draw at Hull City.
In addition, the Frenchman did not travel to Portugal with the rest of the squad for Saturday's friendly against Porto.
"I think it's a cruciate ligament [injury]," Benitez told reporters following the 0-0 draw with the Primeira Liga champions.
"He will need an operation. We need to decide exactly when, but I think we will lose him for a while."
Lejeune was signed from Eibar last summer and made 24 appearances for the Magpies last season.