San Siro Stadium plunged into a shocked silence as Udinese put an unexpected end to Inter's unbeaten run by defeating the table leaders with an incredible 3-1 victory on Saturday night.
The Nerazzurri were undefeated in 16 matches but had shown signs of weakness recently, struggling against Juventus last week and Pordenone in the Italian Cup fourth round. However, they finally succumbed to defeat in humiliating fashion against Massimo Oddo's side.
The hosts conceded the first goal of the match after less than 15 minutes, when Italian striker Kevin Lasagna gave Udinese.
However, Inter fought back quickly and made it all square thanks to their leader, captain and top goalscorer Mauro Icardi, who bagged his 17th league goal just one minute later.
But incredibly enough, the home side let slip two goals in 15 minutes as Udinese took the lead, in the second half, with Rodrigo De Paulo and midfielder Antonin Barak giving the visitors a memorable win.
Luciano Spalletti's men still top the Serie A table but will have to wait for Napoli and Juventus' results this weekend to know about their future.
Both sides contributed to playing an enjoyable first half during, during which Inter had most of the chances but still failed to impose themselves on their guests.
The Nerazzurri went close to scoring after barely eight minutes. On this occasion, Icardi scooped an assist for Ivan Perisic from the right-hand side but the Croatian strike home for Inter.
It was Udinese who managed to break the deadlock first, against the run of play, taking the lead over their hosts with striker Lasagna. The Italian edged past Samir Handanovic after receiving a marvellous cross, and drilled the ball across the six-yard box after stealing it to Davide Santon.
The visitors' lead lasted little more than one minute and Inter equalised to the surprise of no-one through Icardi.
The Argentine scored his 17th goal in 17 matches for the Nerazzurri, as he finished with composure strike from Candreva's delivery.
The game became even more enjoyable to watch following the two early goals and saw both sides try their best to get in front. However, stout defending meant the sides went into the break level.
Inter certainly had numerous occasions to take the lead but Marcelo Brozovic wasted probably one of the best of the home side's chances, as he curled a powerful shot from outside the box which flew wide by inches.
Udinese were often stuck inside their half, rarely managing to push out of their zone and to counter on Handanovic's goal. During the few times when they did it, Oddo's men never managed to create anything impressive and were often too imprecise.
However, deeper into the second half Udinese showed more grit and personality in the opening and saw Handanovic forced into them to save Inter's blushes.
Udinese's new leases of life caught Inter by surprise and the hosts found themselves once again one goal behind, as De Paul converted a penalty around 15 minutes inside the second half.
The visitors were awarded the spot kick after Santon deflected a cross with his hand inside the box. The Argentine taker cannoned the ball towards the top-right corner to make no mistake for for Udinese.
The Nerazzurri were all but happy and counterattacked as much as they could. The San Siro fans looked desperate when they saw Milan Skriniar hit the crossbar with a stunning header just before the half-hour mark.
Roberto Gagliardini too tried to head the ball home for Inter during a corner but his shot was parried by Bizzarri and ended wide outside.
The hosts were left speechless when they conceded their third goal of the day with Czech midfielder Barak, who received a stunning cross from this year's revelation Jakub Jankto and fired home for Udinese to seal a shocking victory.