Host nation Russia will have their credentials tested on Sunday as they are set to come up against 2010 champions Spain in the third round of 16 clash on Sunday.
It is set to be an interesting clash as Russia are the weaker side on paper but the power of being a host nation can propel a country to glory, despite who they come up against.
Spain, on the other hand, have to prove to the world that they are still a powerhouse when it comes to international football after they disappointed in the group stages.
With this in mind, here are three key battles that could very well decide the tie.
3. Diego Costa vs Segei Ignashevic
Diego Costa is easy to hate. He's annoying to play against, he's a nasty piece of work, but most importantly, he's very good.
So far he has been one of the best strikers at the tournament and he demonstrated his strengths against Portugal in particular, where he bullied Pepe and Jose Fonte, to score two goals.
He will be coming up against veteran centre back Sergei Ignashevic. The CSKA Moscow man was called back into the side prior to the tournament despite being 38 years old and so far he has been rock solid.
He lacks any sort of pace, of course. But what he lacks in speed, he makes up in positional awareness and raw strength.
Costa isn't a pacey striker and he prefers to play directly off of defenders. He will be having a hell of a battle with Ignashevic, that's for sure.
2. Isco vs Mario Fernandes
Isco has rapidly become Spain's talisman at this year's tournament due to his inspired performances.
He ran the show against Portugal and he picked his side up after they conceded against Morocco and went on to score a well taken goal. If Isco plays well, Spain tend to as well.
Mario Fernandes will be the man tasked with marking Isco and he has also enjoyed a very impressive World Cup thus far.
He has got forward well to support attacks on a number of occasions but these forward runs will be few and far between when he's having to deal with Isco.
1. Sergio Ramos vs Artem Dzyuba
The ultimate bad boy of world football, Sergio Ramos will do just about anything to make sure he wins. That is what makes him the most accomplished centre back in world football.
Yet, his form wasn't imperious during the group stages and he even made an uncharacteristic mistake against Morocco which cost his side a goal.
Artem Dzyuba has been one of the most unexpected success stories for Russia and he will be a difficult test for Ramos to deal with.
He is an apologetically brutal striker who uses his sizeable frame to rise above defenders and bully them out of the way.
Ramos' job will be to do everything he can to frustrate the Arsenal Tula striker.