Their match against Australia in Adelaide was scheduled for a 7:30pm kick off, nearly two weeks after the start of Ramadan in 2017.
Victory would have all but assured them a place at Russia 2018, but a narrow 3-2 defeat ensured a nervy qualification campaign would go down to the final fixture three months later, with Saudi Arabia narrowly beating Japan to finish second ahead of Australia only on goal difference.
Roel Coumans, conditioning coach to then-Saudi Arabia manager Bert van Marwijk, believes that defeat to Australia was due to the effects of his players' fasting.
'I just simply explained it to the players after the game,' Coumans told CNN Sport. 'I said to them: 'You're going to drive into the desert -- I took a picture of Saudi Arabia -- and 100km further there is an oasis.
'But you only put gasoline in for 50km and then you still expect that you will get to that spot?' And then they understood it.'
Saudi Arabia started the match well, twice coming from behind to go into half-time level. In the second half, however, their performance dropped and Australia scored the winning goal after 64 minutes.
With sunset in Adelaide soon after 5 p.m. in June, the squad -- minus the four players who chose to not observe Ramadan at that time -- were only able to have their first meal of the day about three hours before kickoff.
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'When you're in a top sport you will do everything that influences your performance and I think nutrition is one of the biggest key points for recovery,' Coumans explains.
'But also your energy level and if you have low energy intake, what do you expect? The body has enough for about 45 minutes to an hour and that was exactly what we saw in our performances.
'After an hour we had a break down. We had only four players who were eating for the whole week.'
Despite being unable to eat during daylight hours throughout Ramadan, Coumans says training sessions initially weren't an issue in that international window.
Because of the early sundown in the Australian winter, van Marwijk and Coumans organized training for the players in the evening after they had broken fast at sunset.
However, as the week wore on, the players, unable to maintain their energy levels, instead had to conserve themselves for the match later that week.
'It was more of a problem that you don't recover well in the days after training,' Coumans explains.
'Then they eat but before the next training they don't have enough fuel in their body and that means they won't recover for the next training session and the next session will be less intense.
'Then after seven or eight days there was a match and you don't have enough storage.'
Dino Maamria, a former Tunisian professional footballer who observed Ramadan in his playing days, agrees with Coumans.
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The 47-year-old, now a manager in England, says he wouldn't have recommended the Saudi Arabia players fast in the lead up to the World Cup and doesn't think 48 hours is enough time to refuel sufficiently.
'I don't think it's ideal for them to be fasting in preparation for that,' he told CNN Sport. 'I don't think two days' time will be enough for you to be ready.
'What they can do is train at night time, but it's still not ideal to be fasting and playing football or doing any athletic event. It's not ideal.
'Despite everything, you want your players to produce their best football, you can't do both, especially in an event like the World Cup.'
Knowing how important this holy month is to Muslims, at the forefront of Couman's mind throughout the international break was being respectful towards his players' beliefs, while also trying to maintain their physical well-being to the highest level possible.
Generally, Muslims who travel during Ramadan are exempted from fasting as long as they make up the days later.
'We had a lot of questions before,' Coumans said of his first experience coaching a Muslim national team.'
'The president (of Saudia Arabia's Football Federation) came and said: 'I will bring an Imam in and he will explain to players, don't worry they're going to eat.'
'Then when we were in Australia, there wasn't an Imam and one day nobody was at lunch -- only four players were there, two who were starting (the match).
'It was an unusual situation for us but the coach said: 'I'm not going to force them to eat, it's their religion, I want to be respectful.''
In their first game at Russia 2018, Saudi Arabia fell to a comprehensive 5-0 defeat to hosts Russia -- the only nation in the competition ranked below them -- in what was a disappointing performance.
Saudi Arabia's Football Federation wasn't immediately available for comment when asked about their World Cup preparations during Ramadan.
Sports scientist Dr. Craig Duncan, who is now Coumans' colleague with the Australia national team, believes sleep plays the most vital role in helping fasting players recover.
Unable to replenish their energy supplies with food and drink, rest begins to have an even more important part in eking out every possible ounce of energy.
'It's a very important time culturally and you have to respect that,' he says.
'However, it needs to be managed very carefully from a physiological perspective so the cultural beliefs can be taken into account and respected but also try and get maximum performance out of it.'
'You have to manage the sleep and make sure that you maximize that and use the day to allow them to have naps because there is no doubt the fatigue increases because of the absence of the normal cycle of eating.'
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According to Matt Jones, Saudi Arabia's nutrition specialist during that international window, the players would tend to sleep throughout most of the daylight hours, before breaking their fast with a glass of water and a small meal, usually including dates as is tradition.
They would then train for a couple of hours, before eating a large meal to recover fully. Another smaller meal would be eaten around 1 a.m. and the players would eventually go to sleep around sunrise.
'The big thing is for them to sleep very well. The tendency is for them to go to sleep late and to get into a difficult cycle so we'd just really manage that,' Duncan says.
'If you've got a team that is all practicing or the majority of them then it becomes a little bit easier because you can manage training around the intake of food so it becomes somewhat easier.
'I'd really, really focus on the sleep; the training time and I think it can be done but it's not easy. It's bigger than football isn't it.'
Saudi Arabia open the World Cup against hosts Russia Thursday.
Eid al-Fitr, the religious holiday which celebrates the end of Ramadan, is predicted to fall the day after, the same day Egypt, Morocco and Iran open their World Cup campaigns.
Tunisia, another Muslim-majority country, Nigeria and a host of other Muslim players who play for European countries will play their first matches in the following days.
The day is often celebrated elaborately, with families and friends often sharing large quantities of food.
However, the long-term effects of fasting for a month cannot be compensated for in just 24 hours of regular food consumption.
'I soon realized you can't be at your best if you don't fuel your body,' Maamria adds. 'Getting educated, now I realize it's not possible to do both.
'After Ramadan, your body will take a few days to adjust back to eating again.
'It's very, very difficult to play games as important as a World Cup qualifier or a World Cup game with players who are fasting and have not eaten or had anything to drink for 24 hours.'
Maamria, currently earning his managerial stripes at Stevenage FC in England's fourth tier, recalls the physical shock of trying to continue observing Ramadan when he left Tunisia for England.
With matches during Ramadan in his native league scheduled for 10 p.m., he says the physical effects of fasting were negated sufficiently to still be able to perform at a high level.
'But I remember my first couple of seasons in England,' he tells CNN Sport. 'I was still trying to practice Ramadan and realized very, very quickly that I can't be the best I can be if I'm playing in the morning and afternoon.
'So obviously that affected me and I got to realize that if I want to give my football career all in, I've got to sacrifice Ramadan.
'Scientifically, I realize now, after all the studies, you can't. Actually it's very, very important to fuel your body. Nutrition in football and in sport in general is huge if you want to excel in what you do.'
In England, football clubs tend to train once in the morning, before taking a break for lunch and training again in the afternoon -- sometimes with double sessions.
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While his teammates would refuel at lunch, Maamria was unable to have anything to eat or drink until sunset.
'Matches as well, usually a three o'clock kick off, you can't not eat or drink all day and then start a game at three o'clock and expect to be at your best,' he says.
As Tunisia is a Muslim-majority country and the domestic leagues rescheduled fixtures and training to accommodate Ramadan, Maamria never felt that observing a month of fasting impacted him physically there.
'Obviously there is nobody taking advantage of it because everybody is doing the same,' he says of his home nation. 'But in England it was definitely a disadvantage for me.
'If I'm playing against players that are strong, playing hard and fueling their bodies throughout the week and I'm weak without any fluid in my body, of course I'm not going to react quick enough, of course I'm not going to be at my sharpest.'
But Maamria is well-aware of the mental strength of elite athletes who choose to fast during Ramadan, personally knowing the effort and dedication it takes, and believes it can carry them through.
'I think on the mental side it drives you to be stronger,' he says. 'It takes a lot of guts to fast and a lot of belief in what you're doing.'
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