An explosive start to Russia's 2018 World Cup was guaranteed when the past two European champions Spain and Portugal were paired together in Friday's draw to clash on the second day of the tournament.

World Player of the Year Cristiano Ronaldo will go head-to-head with Real Madrid teammate and Spanish captain Sergio Ramos in the all-Iberian clash in Sochi on the banks of the Black Sea on June 15, before both sides also face Iran and Morocco in Group B.

Whilst in Spain there is fear Ronaldo could come back to bite the hand that has fed him during the past eight years in Madrid, in Portugal the clash was also met with pessimism with a rejuvenated La Roja the side every seeded side wanted to avoid.

"Ronaldo waits for us in Russia," ran the headline in Spanish sports daily Marca's digital edition, whilst their Portuguese counterparts A Bola lamented "Spain is the worst side that could have come out of pot two for the national team".

Both sides of the intense Real Madrid-Barcelona rivalry will be well-represented.

Barring injury, Real's Dani Carvajal, Isco and Marco Asensio should join Ramos in Julen Lopetegui's Spain squad.

Barca teammates will also clash as Portuguese duo Nelson Semedo and Andre Gomes face Gerard Pique, Jordi Alba, Sergio Busquets and Andres Iniesta.

Yet, it is the tension between Ronaldo and Ramos that could rise most in the coming months after a public disagreement earlier this season over Real's stuttering start to the campaign.

Ronaldo complained last month that the departures of Alvaro Morata, Pepe and James Rodriguez had left Real's squad lacking experience compared to the one that claimed a La Liga and Champions League double last season.

However, Ramos, who is seen as a big brother figure to many of the young Spaniards Real have recruited in recent years, later described those comments as "opportunistic".

Portugal will once more look to Ronaldo to carry the hopes of his nation in what is likely to be his last World Cup at 32.

However, after the four-time Ballon d'Or winner limped off injured and in tears early in the Euro 2016 final just 18 months ago, Portugal showed they are much more than a one-man team in shocking hosts France to lift the trophy in Paris.

"They have just won the Euros, they have Ronaldo and also a great team, but we have great hopes and I believe a lot in this Spanish team," former Spain coach Vicente del Bosque told Spanish TV station Cuatro, whilst adding Spain "couldn't complain" about their draw.

Del Bosque's Spain broke Portuguese hearts twice en route to winning the World Cup in 2010 and in a tense penalty shootout in the semi-finals of Euro 2012 when Ronaldo was made to pay for wanting to take the final penalty as his opportunity never came.

"Spain are the natural favourites," insisted Portugal coach Fernando Santos.

However, Spain boss Lopetegui shot down any suggestions his side had been fortunate to avoid the likes of Germany or Brazil from pot one.

"Portugal have won an important title and, moreover, very recently. They are the champions of Europe, they have fantastic players and we are talking about the highest level."

A fast start will be even more imperative to both sides bearing in mind the hammerings they suffered to open their campaign which led to embarrassing group-stage exits three years ago.

Holders Spain were eliminated after just two games following an opening-day 5-1 drubbing by the Netherlands, whilst Portugal never recovered from their own 4-0 thrashing by eventual winners Germany.