"We're thinking about the two friendlies before Portugal. It's possibly the rival which will determine if we go through to the following round, but we've also got to think about the other two opponents," Rodrigo said as quoted by Sefutbol, the official media of the Spanish football team.

Spain, who claimed their only World Cup title in 2010, will take on Portugal in the Black Sea resort of Sochi on June 15 before playing Iran and Morocco in their other two Group B matches.

"It's hard to say how far we'll go. We have to go step by step, starting with the friendlies. We've played well in the qualifiers, but this is the moment of truth," Rodrigo added.

Spain will face Switzerland in Villarreal on Sunday and Tunisia in the Russian city of Krasnodar on June 9 in their last two friendlies ahead of the World Cup,

Russia's first-ever FIFA World Cup will take place from June 14 to July 15 in 11 host cities.