However, after La Roja stumbled to a goalless draw with Cape Verde, they would've taken some hope from that performance, one that Spain manager Luis de la Fuente clearly didn't like, and therefore acted decisively by making four changes to his starting XI.
Four changes for Spain
Out went Marcos Llorente, Ferran Torres, Gavi, and Fabian Ruiz and in came Pedro Porro, Lamine Yamal, Dani Olmo, and Alex Baena.
Spain were unbeaten in 11 games heading into the match, and the last time these two teams met, they eased to a 5-0 victory over the Saudis.
With all four teams in Group H level on one point before the start of play, a win here would put the victors in the box seat for qualification to the Round of 32.
A Saudi Arabian back five was noticeable from kick-off, but they were still unable to stop Lamine Yamal getting the game's first cross into the danger area in the opening minute.
Total domination from the kick-off
The Barcelona man floated in another centre before three minutes were on the clock, and fired a long-range effort goalwards as his colleagues looked to play him in at every opportunity.
85% collective possession for Spain in the opening exchanges hinted at the task ahead of their opponents, who were relegated to clearing the ball anywhere just to stem the flow.
It would take seven minutes for the Saudis to get up the pitch, and as they did so, they looked dangerous, given that most of the Spain XI had set up camp at the other end.
Incredibly, seven La Roja players had a perfect 100% pass completion as the game reached the 10-minute mark, whilst their opponents had already given the ball away on eight separate occasions in the same time frame.
Lamine gets off the mark
Lamine's tap-in at the far post, after a sensational cross from Mikel Oyarzabal, gave Spain their first goal of the tournament, and it set the stadium alight.
It also ended a run of 294 minutes without a goal in the World Cup, their longest since going 236 minutes without scoring from 3rd June 1978 to 11th June 1978, and saw the youngster equal Pele's 68-year-old record of being the only two 18-year-olds to score an opening goal in a World Cup match.
Spain's six touches in the opposition box and 13 final third entries before the quarter-hour (compared to just one and two respectively for Saudi Arabia), were an accurate representation of the action on the pitch, as the likes of Ali Lajami and Moteb Al Harbi were being turned inside out at will.
Only two early one-on-one duels (from nine) were successfully won by the Saudis, who would need to significantly up their efforts if they wanted to get a foothold in the match.
Oyarzabal at the double
Oyarzabal was then denied by Mohammed Al Owais, as Spain continued to swarm all over their opponents, but he soon got his name on the scoresheet with his second shot on target in the game.
Only three minutes later, the Real Sociedad man was again in the right place at the right time to tap home a left-footed volley from two yards out.
With the game already over as a contest, damage limitation became the order of the day for a Saudi side that was woefully out of its depth.
By the time of the first drinks break, the difference in quality was wild. 12 shots to one, 17 touches in the opposition box to one and 13 crosses to none were three (of many) metrics that showed the chasm that existed between the two sides.
Olmo complementing Rodri and Pedri
A stunning effort from Oyarzabal, which grazed the top of the bar, was followed by two attempts from Lamine, the pair having nine between them before the break.
Dani Olmo's 100% pass completion, coupled with two shots at goal, perfectly complemented Pedri's movement and creativity, and Rodri's physicality and dynamism, the latter winning possession back on six occasions, and being successful in both of his aerial duels and five of his seven ground one-on-ones.
Oyarzabal and Lamine would depart at half-time with their respective jobs done, Ferran Torres and Yeremy Pino handed 45 minutes to impress in their stead.
Just four minutes in, another own goal in the tournament, the eighth, made it four for La Roja as Saudi Arabia's Hassan Al Tambakti was the unlucky player to be in the way of Marc Cucurella's close-range drive.
Relentless
Three of Spain's back four won 100% of their tackles, ensuring that their opponents continued to toil for no reward, and the relentless nature of the work ethic of the entire XI will undoubtedly have been one of the most pleasing aspects for de la Fuente.
The concentration levels were also well above average for his side.
For example, young Pau Cubarsi rarely had much to do at the back for La Roja - with 15 minutes to play, he still hadn't had to make a tackle - but he had found his target on 84 of the 85 times he attempted a pass.
In a game that had become nothing more than a training match, that's as laudable as the attacking intent that the Spanish had shown throughout.
An easy night's work for Unai Simon
Abdullah Al Hamdan at least managed to get a shot on target for the Saudis in the closing stages, ensuring Unai Simon had to make one save in the game.
Given that the keeper's only other contribution was to win possession on five occasions, there's some certainty to this being one of the easiest night's work the Athletic Club man will ever have for the national team.
Despite having 22 shots in total, La Roja couldn't add to the scoreline, with Ferran Torres' injury-time strike ruled out for offside.
That is to Saudi Arabia's credit, and although in the grand scheme of things, it meant little, it did show that, belatedly, the players were determined to ensure that their professional pride remained intact, despite a hugely embarrassing opening to this match.
Saudis can still qualify
Even given the manner of the defeat, it's still possible for Saudi Arabia to qualify for the Round of 32.
That's because, if they beat Cape Verde in their final Group H game, they will go through as one of the best third-placed teams in the competition.
Spain, on the other hand, will seek to win against Uruguay to cement their place at the top of the table.