Despite progressing to the 2018 FIFA World Cup Russia™ Round of 16 as group winners, La Roja have not had the same aura about them as during their warm-up friendlies. In particular, there are concerns in the camp over the number of goals they have conceded. Mindful that a single mistake in the knockout stage can mean packing your bags, they are desperate to find the solution sooner rather than later.

Speaking at a press conference, Dani Carvajal did not pull any punches when discussing his side's recent defensive frailties: "The errors have probably been down to lapses in concentration. Portugal scored twice from set-pieces against us. We've got to address our individual mistakes and improve our understanding. If we iron out those kinks, we'll be much stronger in no time."

"We've got to cut down on the defensive mistakes. We've made it far too easy for opponents to score against us, which they've done more because of our errors than their brilliance," added the right-back, who missed his country's opener against Portugal due to injury.

Back to basics? In terms of individuals, Spain have one of the best backlines in the world, but there is no doubt that they have not lived up to their credentials to date. "We can't keep starting so tentatively and giving goals away," said Isco after the Morocco match, before extending his critique to the team as a whole: "We're struggling to control games, which is our bread and butter. We've got to buckle down."

Coach Fernando Hierro is painfully aware that his side need to up their game, as he stressed after La Roja's rearguard was breached repeatedly during the 2-2 draw with which they rounded out the group stage. "We've shipped five goals in three games. We'll get nowhere like that and I've told the players as much."

To put this stat into perspective, this tally is one more goal than La Roja let in altogether across their triumphant campaigns at UEFA EURO 2008 and 2012 and the 2010 World Cup.

Russian artillery looming for Spanish armada Spain's need to quickly solve their defensive shortcomings is heightened by the fact that awaiting them in the Round of 16 are hosts Russia, who are among the tournament's leading scorers so far with eight goals in three games.

However, the Sbornaya are refusing to be lulled into a false sense of security and believe that the Spaniards' troubles at the back have been overplayed. Ilya Kutepov – who is well positioned to comment as a centre-back himself – was categorical on the subject: "Spain's defence? Three words say it all: Barcelona and Real Madrid. They've got [Sergio] Ramos, [Gerard] Pique, Carvajal and Jordi Alba. They've got an incredible embarrassment of riches. I don't think they've got problems at the back. I reckon it's nothing more than a blip," he said.

Nevertheless, Spain remain determined to tighten up, taking their cue from their 2010 success, when defensive solidity provided the bedrock for their run to glory.

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