19:00 BST, Thursday 19 June, Nizhny Novgorod Stadium (Novgorod, Russia), BBC One
When Lionel Messi had his penalty saved by Iceland goalie Hannes Halldórsson, the momentum seemed to fall completely out of the sails of his Argentina teammates.
As they floundered to an unexpected draw, they could take some heart from dominating possession and shot attempts, but the nature of the performance is what will concern Argentinians the most.
Now, game two of the World Cup takes on monumental importance for Argentina as a defeat would likely leave their World Cup dreams in tatters.
Croatia were superb in their game against Nigeria and they already look like they could be booking their place in the last-16 provided they can pick up at least one victory in their final two games.
Last Time Out
Argentina 1-1 Iceland
Sergio Aguero looked like he had set Argentina on their way to victory as he scored before the 20-minute mark with the sort of goal many have come to expect from the Manchester City striker.
Read more analysis on Argentina's draw with Iceland HERE.
Iceland fans could be forgiven at that point in thinking a cricket score could be incoming, but their heart and battle saw them steal an unthinkable point. The heroes of the day were 'keeper Halldorsson and goalscorer Alfred Finnbogason, but really this was a team effort by Iceland.
Messi’s penalty miss dominated the headlines, but really Argentina could look at many missed opportunities and a lack of effort as they squandered a perfect chance to get off to a winning start.
That being said, Argentina did have 27 shots and 78% of the possession, but the resilience of Iceland earned them a well-deserved point.
Croatia 2-0 Nigeria
A drab affair at the Kaliningrad Stadium did at least have two goals though fans of both sides will be worried about their respective poor performances.
An own goal set Croatia on their way to victory, after Oghenekaro Etebo converted Mario Mandzukic's wayward header from Luka Modric's initial cross, before Modric himself netted a penalty on 71 minutes to seal the victory for Croatia.
Read five things we learned on Croatia's victory HERE.
Croatia will obviously be delighted with their victory and the fact that they kept a clean sheet will be music to their manager’s ears, but a much-improved performance will be needed if they expect to defeat Argentina.
Jorge Sampaoli is likely to make a few changes after his side's poor performance against Iceland, but do not expect anything too widespread.
Messi and Aguero will still start in advanced positions, but Ever Banega could come into the side for one of Javier Mascherano or Lucas Biglia. Since Biglia is not quite yet match fit, it could be him that gets dropped.
Luka Modric and Ivan Rakitic represent Croatia's two best players and their midfield partnership is unlikely to be broken up at this tournament unless injuries or suspensions occur.
Croatia will be without former Blackburn Rovers striker Nikola Kalinic after he was kicked out of their World Cup party after refusing to come on as a substitute against Nigeria.
Against a weak Argentina midfield, Zlatko Dalic could select Mateo Kovacic instead of one of Ante Rebic or Andrej Kramaric and switch to a 4-3-3 to exert even more midfield control.
Key Battle: Sergio Aguero (Argentina) vs Dejan Lovren (Croatia)
These two players have battled each other many times over the years in the Premier League though this will be the first time they have ever met in an international game - Lovren did not play in the friendly between the two sides in 2014.
In the Champions League battles between Liverpool and Manchester City, Aguero did not play due to injury, but they did face each other at Anfield in the Premier League when Liverpool ran out 4-3 winners.
Lovren knows that keeping Aguero quiet will be a hard job, and he may have his attention focused on Messi, but it will be important for Croatia to neutralise both if they want any chance of winning.
On the flip-side, Aguero scored against Iceland and will have confidence heading into this game. He has the creativity of Messi and the freedom of not being as closely watched due to the presence of his other attacking teammates.
Will Messi rise to the occasion?
With Argentina, it seems like all we talk about is Messi. That microscope has increased tenfold since his penalty miss against Iceland, and now we are awaiting a reaction from the Barcelona star.
The 31-year-old is forced into the centre of attention given the lack of quality around him and he's asked to do much. Not only is he the goal scorer, but also the playmaker as well as the midfielder looking to start attacks from the edge of his own box.
There's plenty of pressure already on his shoulders without an opening game draw to add to it.
Will he respond with a tantalising performance? Or will he again flatter to deceive? A Cristiano Ronaldo hat-trick has already turned this World Cup partially into yet another Messi vs Ronaldo debate, and a big performance against Croatia will go some way in ending it.
Can Croatia qualify as group winners?
A win against Argentina would more or less confirm Croatia as the winners of this group, a scenario not many people would have predicted before the tournament started.
If they can defeat Argentina, then their passage into the knockouts will be all but confirmed and they could even rest some of their star players in their final game against Iceland.
A defeat would not be the end of the world for the team so this can be treated as a free swing by Zlatko Dalic’s men. In doing so, the pressure on this fixture is all on the Argentines, with Croatia free from its tightening grip.
Prediction: Argentina 2-1 Croatia
It seems inevitable that Argentina will bounce back against Croatia simply because of the firepower they have in their squad.
Their record in qualification was admittedly shaky, but the team will surely come good against Croatia?
Croatia can look at this game as a free swing to get qualification, but really they will know their hopes will rely on defeating Iceland in their final group game.
Listen to the RealSport football writers discuss all the action from Day 5 of the World Cup in Kremlins in the Basement: RealSport’s daily World Cup podcast.