Inter Milan suffered a damaging 1-0 defeat at Bologna on Sunday which virtually ended their slim hopes of winning the Serie A title.
At the same ground where their title aspirations were dealt a fatal blow last season, Riccardo Orsolini's goal condemned Inter to another loss.
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Simone Inzaghi's team are second on 47 points from 24 matches, 18 behind leaders Napoli who beat Empoli 2-0 on Saturday.
Inter will also be looking over their shoulders with concern at AC Milan and Roma, who are level on 44 points and are yet to play in this round of fixtures. Bologna are seventh on 35 points.
Bologna thought they had taken the lead at a rain-sodden Stadio Renato Dall'Ara through Musa Barrow in the 12th minute, only for the effort to be ruled out following a VAR review.
Minutes later, Roberto Soriano rattled the woodwork on the rebound after Andre Onana had parried Andrea Cambiaso's volley into his path.
Inzaghi, missing Federico Dimarco, Milan Skriniar and Joaquin Correa through injury, rested Nicolo Barella among a raft of changes from their midweek Champions League win over Porto, and his much-changed Inter team lacked fluidity.
They had brief spells of possession in the first half, but created few clear-cut chances as Lautaro Martinez headed an Alessandro Bastoni cross just wide of the target and Henrikh Mkhitaryan twice fired over the bar.
Bologna continued to press forward after the break, and Andre Onana kept his side in the game with two crucial saves in quick succession, getting a hand to a Soriano shot before smothering Dominguez's effort from the edge of the area.
Romelu Lukaku and substitute Edin Dzeko each had a shot on target, but it was Bologna who broke the deadlock in the 76th minute when Orsolini raced on to Jerdy Schouten's pass and powered a shot into the net.
"An incredible match in which many things happened. They cancelled a goal for us, we put Inter down by playing really well and we are satisfied," Orsolini told DAZN.
"Schouten put a ball to me, I took advantage of the bounce to bring the ball forward with my chest and in front of Onana I tried to place it under the crossbar."
In April last year, Bologna recorded a 2-1 home win over Inter, which gave the Nerazzurri's rivals AC Milan the momentum in the title race.