Juventus dropped points in Serie A for the first time this season as Genoa held them to a 1-1 draw in Turin on Saturday.
Cristiano Ronaldo's first-half strike was cancelled out by Daniel Bessa as the visitors ended a five-game top-flight losing streak at the Allianz Stadium.
The result gives Napoli the chance to close to within four points of Juve at the top of the table and sees their 11-game winning run in all competitive competitions come to an end just three days before they face Manchester United in the Champions League.
Ronaldo received a player-of-the-month award before kick-off and continued his good recent form with the opening goal, becoming the first player to score 400 goals in Europe's top-five leagues in the process.
But Bessa's header rescued a draw after some slack Juve defending and means Massimiliano Allegri's side no longer have a perfect record in 2018-19.
Ronaldo looked a threat from the off, forcing Ionut Radu into a good save before rattling the woodwork with a powerful header.
He eventually found the net 18 minutes into the game, tapping home from inside the six-yard box after Radu had been wrong-footed by Joao Cancelo's deflected shot.
Juve seemed eager to score a second as soon as possible, but struggled to convert their possession into meaningful chances, and Wojciech Szczesny had to be alert to deny Krzysztof Piatek an equaliser from distance.
Genoa's growing confidence was rewarded after 67 minutes. Christian Kouame picked up a loose ball when Juve's defence assumed it was going out for a corner, and his cross was met by the unmarked Bessa, who headed home from six yards out.
Allegri introduced Paulo Dybala off the bench and both he and Miralem Pjanic fired narrowly wide from distance, but Genoa withstood the late pressure to move into 10th in the table and give Napoli the chance to close the gap to the leaders.
What it means: Juve confidence knocked ahead of United trip
Allegri's side had won 11 games in a row in all competitions before Saturday's game, but they have only themselves to blame for failing to claim their ninth Serie A win of the season here. They seemed to become complacent after going ahead and Genoa deserved their equaliser, a goal that means Napoli could close to within four points of the leaders if they beat Udinese. It also offered United a glimpse of vulnerability ahead of Tuesday's tantalising showdown at Old Trafford.
Cancelo fast joining the elite
Joao Cancelo is improving rapidly in Turin and produced another hugely effective performance. It was his run and shot that led to Ronaldo's opener and he largely stuck to his task well down the right, even as several of his team-mates seemed to switch off.
Bonucci pays price for complacency
Leonardo Bonucci had not had a great deal of defending to do, but the Juve defence were punished for the bizarre moment when they expected the ball to run out of play in the build-up to Bessa's goal. The Italy centre-back has to take a sizeable portion of the blame, though, as he failed to react in time and could only stand and watch as Bessa ran behind him to meet Kouame's cross.
Key Opta stats:
- Juventus have scored more first-half goals than any other team during Serie A this season, while Genoa have conceded more than any other (11) in the same period.
- Genoa's starting 11 is their youngest in Serie A this season.
- Christian Kouame is the youngest player in Serie A this season to create more than two assists.
Juve will now head to the north west of England to prepare for that Champions League showdown with United at Old Trafford. They then travel to Empoli in Serie A next Saturday. Genoa have eight days to prepare for Udinese's visit to the Luigi Ferraris.
|Irving thrives on ´peace´ of being in the zone|
|Lloris admits France could have lost by more|
|Dybala impressed by Argentina´s improved spirit|
|Arsenal chief confirms Super League talks|
|Hooker knocks out Saucedo to retain WBO strap|
|NBA wrap: Kyrie Irving sizzles as Celtics beat Raptors in overtime|
|Jimmy Butler aims dig at Timberwolves following 76ers home debut|
|Koeman surprised by dominant Netherlands|
|Southgate rallies England ahead of Nations League decider|
|Chile 2 Costa Rica 3: Waston brace sinks La Roja|
|Tite inspired by Guardiola´s City|
|Argentina 2 Mexico 0: Funes Mori´s header helps to sink El Tri|
|Lovren ready for ´fiery´ England clash|
|Brazil captain Neymar pleased with stern Uruguay test|
|Ravens´ Flacco doubtful, Jackson could start|
|Richarlison: I want to be at the Copa America|
|Tabarez buoyed by inexperienced Uruguay|
|Howell fires 64 again to extend RSM Classic lead|
|I´m proud of them - Giggs still upbeat despite Denmark defeat|
|Mancini ´very sorry´ for Ronaldo absence|
|Neymar clinches anything-but-friendly win for Brazil over Uruguay|
|Cipriani-inspired Gloucester thrash Tigers|
|Djokovic makes it three wins from three at ATP Finals|
|Germany relegated from Nations League top tier to cap miserable 2018|
|Fulham will back Ranieri in January transfer window if required|
|Brazil 1 Uruguay 0: Neymar penalty settles tight contest|
|Netherlands 2 France 0: Wijnaldum & Depay decisive as Germany are relegated|
|Wales 1 Denmark 2: Jorgensen and Braithwaite seal Nations League promotion|
|Oxlade-Chamberlain targeting early return|
|New Zealand-born Aki will ´relish´ facing All Blacks – Marmion|
|Portugal cannot focus on absent Ronaldo - Santos|
|Ramsey reiterates he wants to stay with Jaguars despite cryptic tweet|
|We tried to hit a home run and it didn´t work out - D´Antoni explains Carmelo exit|
|West Ham´s Zabaleta backs Premier League´s VAR introduction|
|Southgate eyes winning end to England´s ´brilliant year´|
|Patient Zverev seizes opportunity to make amends at ATP Finals|
|Rodgers: Packers still believe they can make playoffs|
|Mahomes hoping to ketchup to Heinz´s touchdown target|
|Ranieri tells Fulham fans not to expect repeat of Leicester ´fairytale´|
|Brown to leave role as RFU chief executive|
|Croatia star Rakitic ruled out of England clash|
|Capital gains for Zverev as he secures last-four spot in London|
|Sancho rise continues with Player of the Month award|
|Jones-Buchanan, Ablett and Briscoe sign new Rhinos deals|
|Root leads from the front as aggressive England assume control|
|Croatia´s Lovren antagonises Ramos and ´rude´ Spain|
|Rakitic has ´enormous respect´ for England ahead of Nations League decider|
|Ireland make flanker switch with Leavy out of All Blacks clash|
|Pakistan rip through Black Caps in Abu Dhabi|
|WATCH: Barcelona mark 15-year anniversary of Messi´s first match|
|Sterling, that you? - Walker uses falling fan to poke fun at England team-mate|
|Fleetwood applies pressure on Molinari, Wallace leads in Dubai|
|Don´t talk to me about VAR – Rakitic not over World Cup final loss|
|Van Dijk leadership essential for Liverpool – Wijnaldum|
|Dalic: Croatia´s bench was ready to stop Spain!|
|Sublime Root century gives England imposing lead|
|Vinicius appreciates Solari influence at Real Madrid|
|Havertz would suit Bayern Munich – Kimmich|
|Wilder: Roach recruitment a sign of Fury nerves|
|Ranieri targets defensive improvements at failing Fulham|
|PSG close investigation into player recruitment practices after finding no discrimination|
|Mayweather: Nasukawa exhibition back on|
|Witsel: Joining Borussia Dortmund my best career decision|
|Ballon d´Or win would not change Modric´s ´best year´|
|Ireland v New Zealand: Opta stats behind the meeting of the world´s top two|
|The Breakdown: A statistical look at Saturday´s rugby internationals|
|Batshuayi dismisses reports of Valencia departure|
|Brazil must make Copa America final – Tite|
|Rockets rout Warriors as Green goes scoreless|
|Seahawks rally past Packers|