Portugal begin their journey in Russia against a Spain side in disarray after manager Julen Lopetegui was sacked just 24 hours before the start of the World Cup.
Fernando Santos' men come into the World Cup as one of the lesser favourite sides despite winning the UEFA European Championship in France, two years ago. However, they have embraced that label before and will do so this time as well, with the confidence of overcoming their opposition to get their victory.
As for Spain, interim manager Fernando Hierro has a huge task on his hands. The squad reportedly spoke against the decision to sack Lopetegui, after he accepted the Real Madrid managerial post. Despite those protests, the Spanish FA was enraged with their manager's actions and hence made the final call.
Now Hierro has the job to set up his team both physically and mentally for a game, that will be demanding, to say the least.
Portugal come into the game as the more confident side
Group B's first game sees these two old rivals face off against each other once again. The last time Portugal and Spain clashed was at Euro 2012, which resulted in a victory for La Roja after a penalty shootout.
This time, though, Portugal will be confident of their chances of getting a positive result. With an in-form Cristiano Ronaldo leading them in their conquest in Russia, Santos and his men will look forward to the chance of causing further damage to a Spanish camp that is already rattled after yesterday's events.
Portugal have lost just two games in the past year and have remained fairly consistent with their results. After finishing third at the FIFA Confederations Cup last year, they will look to reach the final of the World Cup in Russia and cause a surprise once again.
It is fair to say that certain players in the Portuguese camp will be disturbed by the events unfolding in their careers as well. The shocking turn of events at Sporting CP has left several players with question marks over their club futures. It is up to Santos and his staff to make sure his players are in the right state of mind to take on a quality team in Spain.
Gonçalo Guedes will look to hurt the Spanish defenders that he has substantial experience against, from his loan spell at Valencia CF.
Portugal's form in their qualification group was exceptional. After the first loss against Switzerland in his group, Santos and his men recovered to claim the top spot in the group and attain direct qualification.
Ronaldo and co. scored an impressive 32 goals in 10 games, however, repeating that tally once again at the World Cup will be a different kind of challenge.
La Roja looking for calm in the chaos
As Spain prepare for their first game at the World Cup, they will need more mental strength than ever to show that they're capable of challenging for glory in Russia.
Leaders like Sergio Ramos, Gerard Piqué and Andrés Iniesta will have a huge role to play in the coming weeks to galvanise this Spain side and assist Hierro in his duties, as he aims to find some calm in all this chaos.
Before getting sacked, Lopetegui's Spain had a hugely impressive record in their journey to Russia. They cruised through their qualification group unbeaten and scored 36 goals in the process, while conceding just three.
Those kinds of numbers showed that Lopetegui managed to get the right blend of creativity and defensive solidity in the Spain side, which made the Spanish FA's decision to sack him, all the more surprising.
La Roja will look to their world-class midfield to dominate their games and outplay their opposition. Iniesta is coming close to the end of his career and will look to have one last hurrah with his compatriots.
With players like Isco, Marco Asensio, Thiago and Koke, Spain's midfield has the right balance of creativity, attacking threat and defensive intelligence to control games from the middle of the park. It is up to their forwards to score the goals when the chances come.
Spain's midfield will look to Diego Costa to provide the goals, as well as Iago Aspas and Rodrigo who will provide a different kind of threat as compared to Costa in attacking areas.
Spain vs Portugal is a fixture that has a long history attached to it that stretches back the early 20th century when La Roja beat their rivals 3-1 on 18 December, 1921. While Spain's results in this fixture have been largely positive in the past, this time it could well be different.
Both sets of players will have a lot to play for in this game. For Spain, it is to prove their mettle and play with pride in times of difficulty. As for Portugal, they will look to establish themselves as favorites from the outset and beat the odds once again.