European champions Portugal will begin their World Cup qualifying campaign without injured Real Madrid forward Cristiano Ronaldo. The 31-year-old is Portugal's record goalscorer but his international team-mates must cope without him for the away match against Switzerland on September 6.Ronaldo continues to recover from the knee injury he sustained early in the Euro 2016 final, in a clash with France's Dimitri Payet.Portugal head coach Fernando Santos named a 24-man squad on Friday for the Switzerland trip, which is preceded by a home friendly match against Gibraltar - the team's first fixture since landing their first major trophy.That encounter takes place at Boavista's Estadio do Bessa XXI home in Porto next Thursday - September 1 - and could see a debut for striker Andre Silva. Silva was called in by Santos, who believes the 20-year-old Porto striker can serve as a "more classic number nine" than some of his other options. According to Portuguese football website O Jogo, Santos said Portugal have not decided what shape their attack will take for the coming campaign. "Nothing changes with respect to what we want," he said. "A strong unit in defence, pushing as high as possible, which favours an organised attack. What could change is the structure. Whether we play with two mobile forwards, or with a main striker, it will be discussed within the technical team." As well as Ronaldo, Portugal are without defenders Vierinha and Ricardo Carvalho from the squad that triumphed in France last month. Valencia's Joao Cancelo and Zenit St Petersburg's Luis Neto swell the defensive ranks, with Monaco forward Bernardo Silva also promoted into the squad after missing out in the summer. As well as Switzerland, Portugal's World Cup qualifying opponents are Hungary, Faroe Islands, Latvia and Andorra. Portugal squad: Lopes (Lyon), Eduardo (Chelsea), Patricio (Sporting Lisbon); Alves (Cagliari), Cedric (Southampton), Eliseu (Benfica), Cancelo (Valencia), Fonte (Southampton), Neto (Zenit), Pepe (Real Madrid), Guerreiro (Borussia Dortmund); Adrien (Sporting Lisbon), Gomes (Barcelona), Pereira (Porto), Mario (Sporting Lisbon), Moutinho (Monaco), Sanches (Bayern Munich), Carvalho (Sporting Lisbon); A Silva (Porto), B Silva (Monaco), Eder (Lille), Nani (Valencia), R Silva (Braga), Quaresma (Besiktas).