Inter Milan slumped to a fifth successive game without a win as rock-bottom Novara walked away from the San Siro on Sunday with a stunning 1-0 victory.
Andrea Caracciolo scored the only goal of a game in which the hosts never really got out of second gear.
Inter have now lost four out of those last five games, including their Italian Cup defeat by Napoli.
Before that they had put seven wins in a row together but Claudio Ranieri's side have lost their way and remain six points off the final Champions League qualification place.
"It was a difficult game against an in-form team who kept it tight and countered," said Ranieri about Novara, who had not won in 10 games ahead of this meeting.
"We dominated but we didn't score any goals, whereas Caracciolo, unfortunately, scored a great one. No-one held back, everyone showed commitment and application but we're going through a difficult period.
"But if we keep calm and work hard we'll get out of it, as we did a while back."
Inter had already suffered a disastrous start to the season in which they won only two of their first nine league games.
They had turned that around with nine wins out of 10 but with one point from 12 in their last four games in the league, they are going to have to start all over again.
"We had 20 shots, although admittedly many were off target, and we hit the woodwork for the 13th time this season," added Ranieri. "Things didn't go well."
Novara remained bottom despite the win but are at least level on points with Cesena above them and now only four points from safety.
"I'm happy for the team and the fans. We've given ourselves a chance (of survival) from a game that no-one expected us to win," said the match-winner.
"They're great players, they had more of the ball but we did really well."
Following last week's disastrous 4-0 capitulation at Roma, Ranieri shifted things around, playing Diego Milito as a loan frontman with Dutch playmaker Wesley Sneijder and Argentine Ricardo Alvarez behind him.
A slick move on nine minutes saw Alvarez combine with Esteban Cambiasso and set up Sneijder, whose curling right-foot effort was saved at full length by away goalkeeper Samir Ujkani.
Inter were labouring to put any sustained pressure on their visitors but dominated the game nonetheless.
A great move down the left between Cristian Chivu and Sneijder saw the Dutchman's centre across the face of the goal travel just a yard too far in front of the on-rushing Milito.
Alvarez created another chance for Sneijder on 37 minutes as he picked out his team-mate but the Dutchman's low shot was saved by Ujkani at his near post.
Santiago Garcia then made a last-ditch tackle to deny Andrea Poli as the Inter midfielder was about to pull the trigger, although he was guilty of not taking the chance first time.
Novara stunned their hosts 10 minutes into the second period when Caracciolo created space outside the box and curled a sumptuous left-foot effort around goalkeeper Julio Cesar.
Inter were creating little and Cesar was forced into making an awkward save to push away Michel Morganella's bouncing volley.
Novara's Ivan Radovanovic was then dismissed for a second yellow card after kicking the ball away.
Inter found some urgency late on and Sneijder ran across the edge of the box before cracking a shot onto the bar, with substitute Giampaolo Pazzini crowded out on the follow-up.
In other games, Pablo Barrientos scored a brace as Catania thumped Genoa 4-0, while Atalanta and Lecce played out a 0-0 draw.