Florian Lejeune is sidelined with a knee injury at Newcastle United.
The defender sat out last night's 2-2 draw against Hull City at the KCOM Stadium.
And Lejeune is being assessed ahead of Saturday's friendly against Porto at the Estadio do Dragao.
A number of players missed the friendly game, though Lejeune's problem is potentially more "serious".
Asked about absence at Hull, United manager Rafa Benitez said: "Some of them have little problems, and Kenedy’s wife has had a baby, so he has had some time off.
"The only one that is a bit more serious could be Lejeune. He has a knee problem that we have to assess in the next couple of days."
Lejeune played in last week's 2-0 win over St Patrick's Athletic.
Newcastle this week sold defender Chancel Mbemba to Porto.
Josef Yarney, 20, has started United's first two pre-season friendlies.