What's it like to be on the winning team of a massive World Cup upset like Saudi Arabia vs. Argentina?

LUSAIL, Qatar -- For a competition that's usually won by a global heavyweight, the World Cup is still the place for shocks. But even in a tournament that can throw up one or two surprises, Saudi Arabia's 2-1 victory over Argentina on Tuesday still managed to stun the planet.

The result at the Lusail Stadium was so unexpected that it immediately started the debate about whether it is now the World Cup's biggest upset of all time. Cameroon, who beat holders Argentina in 1990, or Senegal, who got the better of reigning champions France in 2002, might have something to say about that over time, but Herve Renard's side are now very much part of the conversation.

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"We made history for Saudi football; it will stay forever," Renard said. "When you are coming to the World Cup, you need to believe in yourself. Everything can happen in football."

Lionel Messi's response was one of shock -- he said his Argentina side were "dead" after Tuesday's result -- and respect for the underdogs who took down one of the presumed favourites to win it all.

"We knew that Saudi Arabia is a team with good players, that they move the ball well and that they push the [defensive] line a lot. We worked on it, but we rushed a bit. We have to go back to the base of who we are. We have to think about what's next."

"I am very happy about this result that we have been able to obtain against this very storied team," said Saudi Arabia goalkeeper Mohammed Alowais. "We have prepared ourselves. We were 100% ready and hopefully we will have better results in the future. I felt we were especially good in the last minutes because we secured our three points."

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According to sources, Saudi Arabia are putting part of their success down to their preparation after securing what they believe is the best training ground in Qatar at Sealine Beach. The facility about an hour's drive south from Doha was secured more than three years ago, long before the other qualifiers began their scramble for hotels and pitches. As a squad picked exclusively from their domestic league, they were also able to play four warm-up games over the past month before kicking off their World Cup. In contrast, Argentina, who still had players competing in domestic games around Europe on Nov. 13, managed to fit in just one fixture against the UAE.

Saudi Arabia, ranked 51st in the world, still probably didn't expect much from their opening game against one of the pre-tournament favourites, but the statistics suggest they had every reason to eye a place in the knockout rounds even before arriving in Qatar.

It's not unusual for teams to qualify for the last-16 after being seeded third or fourth in their groups. At the last World Cup in Russia, Denmark, Sweden and Japan all progressed despite being seeded outside the top two while five of the eight top seeds failed to win their groups.

Holders fare even worse. The World Cup hasn't been retained since 1962, and in the past 14 tournaments, the reigning champions have only reached the semifinals of the next edition twice. France have arrived in Qatar as holders knowing that four of the past five past champions have been knocked in the groups.

In 2010, New Zealand managed to pull off one of the greatest World Cup shocks by holding champions Italy, who finished bottom of their group, to a 1-1 draw. Similar to Saudi Arabia, Ricki Herbert, who coached the Kiwis in that tournament, told ESPN that the key to getting a result against one of the world football's heavyweights is the preparation.

"We looked at the potential areas we believed we could exploit and maximise the strengths that we could offer on the night," he says. "Confidence, belief, courage and discipline were some of the key elements. We wanted to start the game well and to ensure that we made it difficult for the Italy team to settle into any comfortable position. We didn't want to give them the opportunity to start to strongly dictate the game.

"It was certainly an outstanding performance by the team across the full 90 minutes, and a result that made New Zealand a household name across the footballing world. Personally, it was an extremely proud moment."

Aliou Cisse, who played for Senegal in their 2002 opener against France in South Korea and is now managing his country in Qatar, says part of the strategy has to be about accepting that you cannot go toe-to-toe with teams filled with some of the best players in the world.

"You have to defend well and be good with the ball when you get it," he said ahead of his team's defeat to Netherlands on Monday. "But you have to defend when you have to defend."

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Saudi Arabia certainly did that against Argentina, showing just why they were able to keep six clean sheets during qualifying and topped a group that included Japan and Australia despite scoring just 12 goals in 10 games. Renard said after victory over Argentina that he would give his players just "20 minutes" to celebrate, although some got a head start by playing music through portable speakers as they came grinning through the mixed zone.

"A good celebration for 20 minutes and that's it," said Renard. "There's still two games, or more, for us. We need to think about looking forward because we still have two very difficult games [against Poland and Mexico]."

Saudi fans have travelled across the border into Qatar in their thousands, hopeful of seeing their team match, or even better, their performance in 1994 when they reached the last-16 and, if they get there, they will now fancy their chances against anyone. King Salman even declared Wednesday a public holiday in Saudi Arabia, a royal order recommended by Crown Prince Mohammed bin Salman, so the country could celebrate.

In 2018, Russia knocked Spain out in the second round despite sitting 60 places below them in the world rankings. It's still the biggest upset in the knockout rounds since FIFA implemented a ranking system and a reminder that, at a World Cup, anything can happen. Just ask Argentina.