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.
|Youthful Netherlands have forged strong bond - Wijnaldum|
|Premier League confirms £5m package for departing chief Scudamore|
|Thiem blasts past Nishikori to keep semi-final hopes alive|
|He´s always got time for me – Gerrard loved learning from Liverpool boss Klopp|
|Kearney and Ringrose return for All Blacks clash|
|Molinari on course for Race to Dubai title, Smith and Otaegui lead|
|Premier League to implement VAR from 2019-20 season|
|FSF urges Premier League clubs to reject Scudamore ´golden handshake´ request|
|Rhinos pull off Merrin coup|
|Ribery apologises for reporter altercation|
|Ford to captain much-changed England, Cokanasiga starts|
|Crotty replaces injured Williams for Ireland showdown|
|Classy Roshen gives Sri Lanka unlikely lead|
|Injured Lukaku out of Belgium-Iceland Nations League clash|
|Rooney ´passionate´ about future coaching career|
|Mehidy spins Tigers to victory despite second Taylor hundred|
|Rooney deserves special England day - Antonio|
|LeBron thinks back to his roots after latest milestone|
|Messi to return for Argentina next year - General manager Burruchaga|
|Walton salutes LeBron after he surpasses Chamberlain|
|Croatia´s Dalic and Modric not out for Spain revenge|
|Rondo to miss ´a few weeks´ with broken hand|
|Gabi, Juanfran hopeful over Oblak´s Atletico future|
|England rookie Wilson not comparing himself to Kane|
|WATCH: The baskets that moved LeBron James up the all-time NBA scoring list|
|LeBron moves into fifth on scoring list, 76ers fall in Butler´s debut|
|LeBron James into top five NBA scorers: Five quotes from league legends on his greatness|
|LeBron passes Chamberlain for fifth on all-time scoring list|
|Butler: 76ers need time to gel|
|South Africa lose 28-9 in Windies defeat|
|Delph impressed by ´special´ Sancho|
|Bolt may give up on football career despite ´a lot of offers´|
|We´re better than Dortmund – Wagner urges Bayern to respond|
|Raptors fans give former coach Casey standing ovation in return|
|Martinez hails Hazard leadership|
|Muller going through ´difficult´ period, says Low|
|Betances wants Yankees to sign Machado|
|Rays´ Snell, Mets´ deGrom win Cy Young Awards|
|Dinwiddie to debut Stan Lee-inspired shoes against Heat|
|Iberostar Tenerife and Segafredo Virtus Bologna stay perfect in BCL|
|Rooney wanted to finish career at Manchester United|
|Red Sox give manager Cora contract extension through at least 2021|
|WATCH: Ronnie O´Sullivan hits blue with calamitous break-off shot|
|Matuidi: Mbappe has a great personality, like Ronaldo, Messi and Zlatan|
|Cilic beats Isner to hand Djokovic semi-final spot|
|Mendy undergoes knee surgery|
|Warriors´ Curry will not play during three-game road trip|
|Ramos refuses to retaliate after Lovren jibe|
|Qatar pull off shock win over Switzerland|
|Tuilagi could make England return against Australia|
|Rooney has earned England reward - Sarachan|
|Croatia thrashing means nothing now – Luis Enrique|
|Chelsea and Everton among Arnautovic suitors, claims agent|
|TJ Watt hopes to win NFL sacks race with brother JJ|
|Modric defends Ramos after Lovren comments|
|Southgate hails ´outstanding´ Delph as he talks up England strength in depth|
|No war with Manchester United over Fellaini, insists Martinez|
|Rooney to wear number 10 shirt against USA and receive armband from Delph|
|I don´t feel pressure of Liverpool expectations, claims Klopp|
|Steelers´ Roethlisberger texted Bell but ´didn’t hear back´|
|Reus and Kroos to sit out Germany´s clash with Russia|
|Van Dijk happy to recommend De Ligt if Liverpool ask|
|Sauber announce launch of junior programme|
|No ´breathtaking tennis´ in Djokovic´s win against Zverev|
|Curran: England spinners will be key in Kandy|
|Djokovic charges past Zverev to move closer to ATP Finals progression|
|Messi is a football alien - Malcom|
|Sky´s the limit for Sancho, says Dortmund team-mate Pulisic|
|Radwanska retires from tennis at 29|
|Maybe one day - Pulisic open to Premier League move|