Argentina's 36-match unbeaten run came to a shocking stop at the hands of Saudi Arabia in their 2022 FIFA World Cup opener.Lionel Messi handed La Albiceleste, one of the pre-tournament favorites to go all the way, the lead in the 10th minute from the penalty spot. The South American giants also had as many as three goals ruled out for offside in the first half.However, Saudi Arabia staged a comeback for the ages just moments into the second half. Saleh Alshehri got the equalizer in the 48th minute after an error by Cristian Romero before Salem Aldawsari put the Asian side ahead five minutes later.Having turned the tie on its head, Saudi Arabia then showed incredible resilience and grit to hold on. Argentina had as many as 15 shots and six on target, even seeing a couple of efforts blocked off the line, but couldn't find the equalizer.The FIFA World Cup once again spun its magic and the football community had a wide range of reactions to the spectacle. Legendary Spain and Real Madrid goalkeeper Iker Casillas wrote on Twitter (translated from Spanish):"Surprise in Qatar!! 😳"Iker Casillas@IkerCasillasSorpreson en Qatar!! 205631066Sorpreson en Qatar!! 😳England legend and 1986 World Cup Golden Boot winner Gary Lineker tweeted:"That is one of the greatest upsets in World Cup history. Extraordinary performance from Saudi Arabia."Gary Lineker 💙💛@GaryLinekerThat is one of the greatest upsets in World Cup history. Extraordinary performance from Saudi Arabia.288132991That is one of the greatest upsets in World Cup history. Extraordinary performance from Saudi Arabia.Arsenal legend Ian Wright posted a video of his shocked reaction just moments after Saudi Arabia took the lead:Ian Wright@IanWright087541029https://t.co/X6DiDR5Ib0Here are some more reactions to one of the greatest World Cup upsets of all time:James Olley@JamesOlleyIn FIFA's technical briefing on Saturday, Arsene Wenger actually cited Argentina as an example of a team which could be unbalanced by an injury on the eve of the tournament (Lo Celso). Nevertheless, not sure anybody saw this one coming. Stunning result for Saudi Arabia.18654In FIFA's technical briefing on Saturday, Arsene Wenger actually cited Argentina as an example of a team which could be unbalanced by an injury on the eve of the tournament (Lo Celso). Nevertheless, not sure anybody saw this one coming. Stunning result for Saudi Arabia.Alejandro Moreno@AleMorenoESPNSouth American optimism assemble!!!...maybe this result sends #Argentina to the other side of the bracket opening the possibility of meeting #Brazil in the Final instead of Semis.705South American optimism assemble!!!...maybe this result sends #Argentina to the other side of the bracket opening the possibility of meeting #Brazil in the Final instead of Semis.Melissa Reddy@MelissaReddy_Unreal from Saudi Arabia with their press and brave high line providing one of the World Cup's great shocks. Argentina's 36-match unbeaten run stretching back to 2019 was marked by a sense of calm and surety under Lionel Scaloni. That vanished in the second half.39552Unreal from Saudi Arabia with their press and brave high line providing one of the World Cup's great shocks. Argentina's 36-match unbeaten run stretching back to 2019 was marked by a sense of calm and surety under Lionel Scaloni. That vanished in the second half.John Ogu@ogujohnugoSaudi Arabia win against Argentina reminds me of our win against Spain at France 98 ..435Saudi Arabia win against Argentina reminds me of our win against Spain at France 98 ..Roy Nemer@RoyNemerNo excuses at all but not having Gio Lo Celso for Argentina cut their ability to split the back line through the middle, which is what they needed today. Papu a good dribbler, Enzo very good too but Lo Celso just more direct. A big miss today. 1458117No excuses at all but not having Gio Lo Celso for Argentina cut their ability to split the back line through the middle, which is what they needed today. Papu a good dribbler, Enzo very good too but Lo Celso just more direct. A big miss today. 🇦🇷Tim Vickery@Tim_Vickeryone of the all time great World Cup results - ran the risk of the high line, but wouldn't have won without it - stopped Argentina building rhythm, then win the ball high and strike. A victory for courage54862one of the all time great World Cup results - ran the risk of the high line, but wouldn't have won without it - stopped Argentina building rhythm, then win the ball high and strike. A victory for couragePiers Morgan@piersmorganOops.607726250Oops. https://t.co/8vs8UUTGuyKelly Smith MBE OLY@kelly_smith10What a game that was 🏾🏾 #FIFAWorldCup @IanWright073721What a game that was 🇦🇷🇸🇦😳👏🏾👏🏾 #FIFAWorldCup @IanWright0 https://t.co/cclIAgYvIvArgentina fall flat in FIFA World Cup opener; tougher challenges lie aheadArgentina's at times impenetrable defense has been a hallmark of the team's incredible run of form since 2019. However, their backline came crumbling down on the biggest stage in their 2022 FIFA World Cup opener.Saudi Arabia often caused problems for La Albiceleste's defenders in the first half, but without much success. Lionel Scaloni's men couldn't settle themselves down in the second half either as the Asian outfit hounded them with their high press in the first 10 minutes.Lionel Messi and Co. seemed to lose their composure upon conceding two goals, rushing through many of their forays forward. While they did force a few saves, Saudi Arabia comfortably dealt with most of their opponents' crosses.Argentina now have it all to do in their final two Group C matches against tricky opponents. They will take on Mexico in their second 2022 FIFA World Cup contest on November 26 and Poland on November 30.