On paper, few matches in World Cup history will have been more of a mismatch than Argentina against Iceland.
The two-time champions, producers of some of the best players to ever grace the game, against the debutantes and smallest nation to ever qualify for the tournament.
Argentina 1-1 Iceland
Messi penalty saved
Croatia 2-0 Nigeria
For context, the population of the Buenos Aires province, Argentina's capital, is 45 times bigger than that of Iceland's entire population.
This was David versus Goliath -- and then some.
Not that you'd have noticed -- any notion that the tiny island nation would be overawed by the occasion and their opponents was quickly dispelled, as they went toe-to-toe with Argentina from the first whistle.
Moments after Nicol-s Tagliafico's stooping header flashed inches wide of the post, one long ball over the top -- in an instant exposing Argentina's frailties -- set Alfred Finnbogason free, but the forward couldn't keep his volley down.
Argentina were then almost the masters of their own downfall, gifting Iceland the ball inside their own box in an attempt to play out from the back.
The ball eventually fell to Birkir Bjarnason, scorer of Iceland's first ever goal in a major tournament two years ago in France, but the midfielder somehow skewed the ball wide with the goal gaping.
It wasn't long before Lionel Messi came to the fore, using his customary shuffle inside and left-foot shot to test Hannes Thor Halldorsson in the Iceland goal.
But it was Sergio Aguero, previously without a World Cup goal in his eight appearances, who breathed life into Argentina's campaign.
Marcos Rojo's scuffed shot was controlled superbly by the Manchester City forward, who brilliantly wriggled free of his marker and slammed a shot into the roof of the net.
Cue coach Jorge Sampaoli's trademark wild fist pumping on the touchline, this year swapping his normal casual attire for a sharp suit.
Anyone who had forgotten about Iceland's exploits at Euro 2016 and thought that early goal meant it was game over were soon given a reminder of their fighting spirit.
With Argentina's sloppy defense again exposed, Finnbogason pounced after a scramble in the box to coolly tuck the ball past Willy Caballero.
At halftime, despite having just 21% possession, Iceland had been more than a match for their famous rivals, even creating the best chances in the game.
But the match-changing moment came just after the hour mark. Iceland, having defended resolutely for so long, gave away a sloppy penalty as Hoerdur Magnusson clumsily tripped Aguero in the box.
Up stepped Messi, the man on whose shoulders Argentina have placed their hopes, and -- not for the first time in his career -- missed the crucial spot kick.
Halldorsson guessed the right way and comfortably palmed Messi's penalty away from danger.
Iceland's keeper isn't just adept at keeping one of the world's greatest players at bay.
Just two days before Iceland's training camp started, Halldorsson was in Reykjavik doing some "sidework" -- directing a soft drink commercial in his role as film director where he had previously forged a career.
Before the 90 minutes were up, Halldorsson's lightning-quick reflexes were again called upon as he tipped Cristian Pavon's effort round the post at full stretch.
For all their star power, Argentina were unable to find a way through Iceland's sturdy defense. It's the first time La Albiceleste have failed to win an opening World Cup game since they lost to Cameroon in 1990.
The good news for Messi et al is they still reached the final that year.
Perhaps one of the most telling aspects of the game came after the final whistle, or rather it was what didn't come.
Despite this being their first World Cup, picking up their first ever World Cup point, there was no exuberant celebrations from Iceland, no joyous huddles.
This was just another game, they now feel like they belong here.
Battle of the best dressed
While the on-pitch credentials of Croatia and Nigeria are yet to be decided at this World Cup, one thing everybody can agree on is that they are two of the best dressed teams in the competition.
Nigeria's stylish number sold out online within minutes of its release (while they also won the highly coveted CNN World Cup of Kits title on social media) and Croatia's eye-catching strip is a sleek take on their classic chessboard design.
Unfortunately, neither side could produce football of a style befitting their outfits in what proved to be a tentative opening to the match.
But with Croatia chipping away at its opponent, the game came to life after half an hour as Nigeria's defense crumbled.
Ivan Rakitic's corner into the box was flicked on at the near post by Mario Mandzukic and Oghenekaro Etebo was the unfortunate Nigerian who diverted the loose ball into his own net.
It proved to be the catalyst the game needed, as Odion Ighalo immediately tested the Croatia defense, before Andrej Kramaric looped a header just over the crossbar.
As the halftime whistle blew, Nigeria's players huddled in the middle of the pitch -- and then again when they reemerged from the tunnel.
But their attempts to inject some desire fell flat as Croatia dominated the second half from the start.
For a nation whose fans and players had shown such enthusiasm in the build up to the tournament, Nigeria underwhelmed on its debut in Russia.
The game was over as a contest after 70 minutes, as William Troost-Ekong's decision to grapple Mandzukic in midair from a corner gave referee Sandro Ricci no choice but to award a penalty.
Captain Luka Modric stepped up and buried the spot kick.
Much like the Kaliningrad Stadium, which is built on wetlands in the Russian enclave, Nigeria were slowly sinking.
With Argentina's shock draw against Iceland earlier on Saturday, Croatia will now have real hopes of topping Group D.