Inter Milan handed local rivals AC Milan the advantage in the Serie A title race on Sunday despite snatching a last-gasp 1-1 draw at Torino, as Napoli leapfrogged them into second place with a 2-1 win at Verona.
Alexis Sanchez hit the leveller in the third minute of stoppage time of an entertaining encounter in Turin which left Inter in third, four points behind Milan.
Simone Inzaghi's side have a game in hand, but they are now looking over their shoulders at Juventus, who are only three points behind their old rivals in fourth after stringing together a 14-match unbeaten run.
That would have been unthinkable at the turn of the year when Inter were four points clear at the top and 12 ahead of Juve but Inter are ragged after looking imperious before Christmas.
"We know that we need to do more, have a different approach to these games, if we want to retain the title," Inzaghi admitted to DAZN.
Sanchez's equaliser was laid on by Edin Dzeko, who was Inter's worst culprit in front of goal after heading just wide on the hour and then nodding over from point-blank range moments before his Chilean teammate did the honours.
However Inter could easily have lost in a deeply disappointing display.
After Brazilian defender Bremer gave the hosts the lead with 11 minutes gone, Samir Handanovic brilliantly tipped wide Armando Izzo's free header in the 64th minute.
Seconds before Robin Gosens had saved his goalkeeper with a desperate lunge to stop Josip Brekalo from scoring what would have been a superb individual goal after the Croatian international weaved his wave into the box.
They were also saved by the officials when Andrea Ranocchia was somehow ruled to have not fouled Andrea Belotti in the area nine minutes before the break, a decision which left Torino baffled.
"I went to (referee Marco) Guida and told him that it was a stonewall penalty, and he said to me 'VAR didn't call me so I must have made the right decision'," said Torino's sporting director Davide Vagnati.
"You can talk about our brilliant performance and Inter's determination but if there's a penalty then they have to give it to us."
Victor Osimhen struck the first of his brace for Napoli, which kept them three points behind Milan, in the 14th minute at the Stadio Bentegodi by thumping home a perfect header from Matteo Politano's cross.
In an eventful match for both Osimhen as the rest of his team, at one point it looked as though Napoli would have to do without their star forward for over half an hour when the 23-year-old was out of action for four minutes with a shoulder problem following a clash with Koray Gunter.
He carried on however and lashed in his crucial ninth league goal of the season in the 71st minute before snatching a camera and taking a snap of the Napoli fans.
"(Kalidou) Koulibaly gave me the camera to take a picture of the fans who have been amazing from the blast of the whistle to the very end. I think they deserved to get a shot," he told DAZN.
Verona, whose hardcore fans caused outrage in the run up to the match with a banner which indicated the coordinates of Naples as a bombing target for Russia, had their hopes of continental football next season dented despite Davide Faraoni pulling a goal back shortly after Osimhen's second.
They are seven points behind both Roma and Atalanta who occupy sixth and fifth after their respective draws with Udinese and Genoa.
Atalanta look to have forfeited their fight for the Champions League after a goalless stalemate with struggling Genoa, who have now drawn all seven matches under coach Alexander Blessin.
Gian Piero Gasperini's Atalanta are eight points behind fourth-placed Juventus, albeit with a game in hand.
Both Atalanta and Roma can be overtaken by Lazio, who are two points behind the pair before their match with Venezia in Rome on Monday night.