Moscow: Considering their turbulent start to the FIFA World Cup, Spain will be pleased to have safely negotiated the group phase, even if they are yet to click under interim head coach Fernando Hierro. The 2010 champions probably face their toughest test yet against Russia here on Sunday.
Former Spain international Hierro was named coach on the eve of the tournament, replacing Julen Lopetegui, who was sacked after it was revealed he had accepted an offer to join Real Madrid, reports Xinhua news agency.
Spain played remarkably well in a 3-3 draw with European champions Portugal - just two days after Lopetegui's dismissal - and scraped to a 1-0 victory over Iran before a shaky 2-2 draw with Morocco.
Russia have been one of the surprise teams of the tournament. Ranked 70th in the world by FIFA, Stanislav Cherchesov's side won their opening match against Saudi Arabia 5-0 before disposing of Egypt 3-1 five days later.
They thudded back to earth with a 0-3 loss to Uruguay in their final group match after Igor Smolnikov's 36th-minute red card.
But one senses that the result against the Uruguayans has done little to dampen team spirit as Russia benefit from a groundswell of optimism and support that goes along with being the tournament hosts.
While their defence has looked shaky on occasions, Russia has genuine quality in attack. Spain will be wary of the threat posed by Artem Dzyuba, Denis Cheryshev, and Aleksandr Golovin, who have scored six of Russia's eight goals and produced three assists.
Spain also have no shortage of scoring options, even if there are doubts about who will start up front for them at Luzhniki Stadium.
Diego Costa has been Spain's top scorer here with three goals but there remains a feeling that the 29-year-old, who thrives in a counter-attacking team like Diego Simeone's Atletico Madrid, may not be an ideal fit for Spain.
His battering ram style looks at odds with a side that still prioritizes possession and slick triangular passing, hallmarks of their tiki-taka revolution that delivered two European championships and the World Cup from 2008 to 2012.
The Brazil-born Costa was anonymous for long periods against Morocco, struggling to find pockets of space against the African side's deep-lying defence. The introduction of Iago Aspas, who replaced Costa in the 74th minute, provided Spain with an immediate spark and Hierro might be tempted to start the Celta Vigo player on Sunday, either as a false nine or on a wing.
Hierro also seems undecided about how to set up his midfield, having chopped and changed personnel and formations in the first three matches.
Thiago Alcantara failed to impress in his first start for the tournament against Morocco and an opportunity may be given to Atletico Madrid's Koke against Russia.
The fact that defender Sergio Ramos has completed more passes than anyone in the group stage says a lot about a side that saw a lot of the ball but didn't do much with it.
However, they will hope that Russia will offer them more space than a defensive Iran did. If Russia do open up, the Spanish should have more than enough quality to beat them.
The host nation have a tough task to get past the Spanish, especially after Uruguay exposed their weaknesses in their last group match.
However, Russia can expect help from the 81,000 fans in the Luzhniki Stadium and will also take heart from the fact Spain have never beaten a host nation in a major tournament.
Their best hope will be to play a high-energy pressing game in their own half and look for Denis Cheryshev to exploit spaces behind a Spanish defense which tends to push to the halfway line.