Rafa Benitez is sweating on the fitness of Florian Lejeune ahead of the new season.
The Newcastle United defender has not travelled to Portugal with his team-mates for the club’s friendlies against Porto and Braga.
Lejeune missed Tuesday night’s friendly against Hull City with a knee injury.
United manager Benitez admitted that the problem could be more “serious” than some of the knocks that other players are carrying.
Asked about absences at the KCOM Stadium, Benitez said: “Some of them have little problems.
“The only one that is a bit more serious could be Lejeune. He has a knee problem that we have to assess.”
Benitez also left behind winger Rolando Aarons, though striker Dwight Gayle – who didn’t feature against Hull City – was on the club’s flight.
Newcastle take on Porto at the Estadio do Dragao tonight (8pm kick-off).
The game is followed by a fixture against Braga on August 1.
Benitez and his players will then return to Tyneside for the August 4 home game against Augsburg.