Bayern Munich's young midfielder Renato Sanches has pulled out of Portugal's squad due to a muscle injury.
Sanches, 19, has yet to make his debut for the German champions after joining from Benfica over the summer, and was an unused substitute in the club's 6-0 Bundesliga rout of Werder Bremen last Friday.
Portugal will face Gilbraltar in an international friendly on Thursday, before they their World Cup Group B qualifier against Switzerland on Sept. 6 in Basel.
"Renato is still feeling the injury to his muscle and that prevents him taking part in Portugal's two upcoming matches," said Bayern's club doctor Volker Braun.
The European champions will have to make do without Real Madrid forward Cristiano Ronaldo too, as he continues rehabilitation from an injury sustained in the Euro 2016 final against France.
Goalkeeper Marafona has been called up to replace injured Anthony Lopes who is nursing a shoulder injury.