A goal from Sevilla winger Jesus Navas just two minutes from the end sealed the deal for Spain, who, until that point, were playing a precarious game. They conceded some gilt-edged chances to their opponents, who needed just one goal with the score at 0-0, to win
Of course, it could be said that La Furia Roja knew a point would be enough to progress. They merely focused on retaining possession and limiting Croatia's chances.
Nonetheless, their lack of conviction in the final third and defensive lapses in concentration would've undoubtedly cost them—had they been playing the likes of Germany, Italy or France.
Here are five things Spain will have to improve on ahead of their quarterfinal clash against France, England or Ukraine.
Spain were clearly complacent heading into their clash with Croatia. The team desperately need to improve its attitude in the next game if they are to defend their title.
The Spaniards showed no conviction in attack and played with little urgency, seemingly content to pass the ball around and just rely on their ability to find the perfect opening.
This allowed the tactically and technically-adept Croatians to organise themselves defensively with two banks of four. They were able to prevent Spain from creating the clear-cut chances they have had in previous matches.
It gave Croatia chances to counter-attack in numbers and dictate the tempo of the game whenever they gained possession.
Manager Vicente Del Bosque will need to instil more urgency in his players for their quarterfinal clash to avoid being hurt on the counter-attack.
One thing Spain weren't able to do throughout the match against Croatia was increase the tempo of play.
Every time they tried to create an opening in attack, the team relied on single player movements as opposed to a number of players making runs across the final third.
This gave the opposition the chance to organise themselves positionally and close down the Spaniards quickly every time a shot on goal presented itself.
If Spain are to overcome stubborn defensive resistance from their opponents, they'll need to improve their ability to increase the tempo of the game and attack the opposition before they have the chance to get into position.
Spain need to shoot more often. If they don't, they could end up running out of chances to win the game.
Against Croatia, they waited for the perfect chance to score. In the case of players like Sergio Busquets, they didn't take the opportunities when presented to them.
Every time Spain have a chance to shoot inside the penalty area, they need to take it. In Gdansk on Monday night, their lack of willingness to shoot could've cost them big time.
For all the possessions Spain had, their lack of positioning and concentration on defence could've made for a very deleterious ending.
The fullbacks being so far up the pitch allowed Croatia to get the likes of Mario Mandzukic, Ivan Rakitic, Luka Modric and Ivan Perisic in behind the outside defenders.
The space afforded to them deep inside Spain's half gave the Croatian's the time to create clear-cut chances—with Modric's cross for Rakitic's gilt-edged header being the most notable.
The centre-backs will need to stop ball-watching if they aren't to be undone by stronger attacking line-ups. Perisic's volleyed effort was one big example of when such a mistake could've cost Spain.
Vicente Del Bosque presumably thinks that playing without a recognised striker will give his team more fluidity in attack. Interlinking midfielders making bursts into the penalty give his side that element of unpredictability.
If a 4-6-0 formation is the route he wants to go down, then such a tactic is something that'll need to be worked on extensively in training if it is to work against the top sides.
Otherwise, Spain need to get back to playing with a recognised striker up-front, as the team lacked a focal point in attack when Fernando Torres was taken off and replaced with winger Jesus Navas.
In essence, the Spaniards need to sort their tactics out asap if they are to push on and defend their European Championship crown.