Spain entertain one of the seven teams above them in Fifa’s world rankings tonight in Villarreal – the one which is the biggest surprise.
Switzerland, who have risen to sixth place, have built an impressive squad.
They won nine of their 10 qualifying games – but still finished second in their group to European champions Portugal.
Vladimir Petkovic’s side then beat Northern Ireland in a qualifier to confirm they would be going to their fourth successive World Cup finals, but they need more practice against top opponents ahead of their group with Brazil, Serbia and 2014’s surprise team, Costa Rica.
Switzerland also have injuries, while a number of their players have not been playing regularly for their club sides, most notably captain and sometime Juventus right-back Stephan Lichtsteiner.
Spain may be eighth in Fifa’s rankings, but they are one of the major contenders to triumph in Russia at the World Cup.
Julen Lopetegui, the Spain manager, is calm, seldom interesting and not the character that his predecessors Luis Aragones or Vicente del Bosque were, but he is respected by players for his attention to detail and planning.
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The former goalkeeper, 51, is also yet to lose as Spain chief, both for the full national side and the under 21s. He led Spain’s under 19s and under 21s to European championship success and optimism is high that he can triumph with the full national side.
The recent 6-1 victory against an Argentina without Lionel Messi in Madrid certainly created much optimism and Lopetegui has tried to calm the euphoria, but Spain are packed with top-level talent.
A few days before drubbing Argentina, Spain drew in Germany. They also won their tough qualifying group with ease, leaving Italy trailing by five points. Italy were the biggest surprise omission from Russia.
Spain have experience throughout, with Sergio Ramos, Sergio Busquets, David Silva, Andres Iniesta and Gerard Pique amongst others heading to their third or fourth World Cup finals.
David de Gea, 27, is joining them in his first as the No 1 goalkeeper. His two Manchester United teammates Juan Mata and Ander Herrera didn't make the squad, showing how much quality Spain have, but De Gea is finally Spain’s first choice after playing second fiddle to Iker Casillas.
He has been around the squad a long time and he also played with Koke, Isco, Sergi Roberto and Nacho for Spain’s under 21s.
Iniesta, 34, will likely retire from international football after the tournament. The man who scored the winning goal in the 2010 final recently moved to Japan, but remained effective as a Barcelona player this season and can supply a forward with passes of the highest quality.
Spain have often played without any obvious striker, but an in-form Diego Costa, now back at Atletico Madrid, can be a huge asset.
He usually has Iniesta, Isco and Silva behind him. Koke and Busquets are the two in a 4-2-3-1 formation, with Jordi Alba, Pique, Ramos and Dani Carvajal in defence.
Lopetegui has varied the formation, using a false nine like his predecessors and using three central defenders.
Spain still play the attractive, pressing and possession-heavy football which made them European champions in 2008 and 2012 and won the World Cup in 2010.
They will not be overconfident after the disappointment of the 2014 World Cup when they failed to get out of their group, but they also have hugely talented younger players ready to step up, including Real Madrid’s Marco Asensio.
Up front, striker Rodrigo has been rewarded with a call up after his sparkling form for Valencia and while Iago Aspas did little during his spell in England with Liverpool, he has been consistently impressive for Celta Vigo.
Spain will fly to Russia after the friendly, where they wll be based in Krasnodar, 1,300 kilometres south of Moscow.
No team will travel as much as Spain’s 9,300 kilometres in the first stage where they play Iran, Morocco and European champions Portugal in Group B, but at least they will not have to go far for their final friendly against Tunisia in Krasnodar on June 6.
But first they meet Switzerland, where the 90 minutes should give the Swiss a clearer indication of where they stand against the major contenders and if their Fifa ranking flatters them or not.