Adolfo Gaich inflicted the latest blow on Andrea Pirlo and Juventus as lowly Benevento snatched a stunning 1-0 win in Turin.
A wretched pass from Juventus midfielder Arthur was seized upon by striker Gaich, who drilled a powerful finish beyond Wojciech Szczesny for the 69th-minute winner.
Coach Pirlo looked askance on the touchline as his team suffered another defeat, with this one leaving them 10 points behind leaders Inter, their hopes of a 10th successive Serie A title in tatters.
They had chances in this game and a penalty decision overturned after a VAR review, but were left counting the cost of one careless mistake.
Cristiano Ronaldo struck a low shot six inches wide of the left post in the third minute, in an early warning from Juventus.
Alvaro Morata, who scored but was also sent off after the final whistle when these sides drew 1-1 in November, was the next Juve player to have a significant sight of goal. The Spanish striker outsmarted the Benevento defence and ran through the centre before his low shot was blocked by goalkeeper Lorenzo Montipo.
Juventus were awarded a penalty in the 35th minute when referee Rosario Abisso thought defender Daam Foulon handled a cross from Dejan Kulusevski, but the official changed his mind after reviewing on a pitchside monitor.
Matthijs de Ligt had a firm header well saved by Montipo, and moments later Ronaldo skilfully volleyed in a cross from Kulusevski but had strayed a yard offside. Ronaldo then tried his luck with a thumping drive from 25 yards, but again Montipo resisted as the half ended goalless.
A drab start to the second half was almost followed by an own goal, with Benevento's Federico Barba turning the latest cross from the right by Kulusevski towards his own goal, with Montipo making a smart reaction save.
Then came the shock of Benevento going ahead, with a terrible pass across the penalty area from Arthur, in the left-back position, intercepted by Gaich. The Argentine striker fended off a weak challenge from Danilo and rammed the ball into the bottom left corner.
Ronaldo failed to put away a late half-chance and Danilo fired over from close range as Juventus scrambled to get back in the game, but it was not their day.
What does it mean?
The battle of the benches between former Milan team-mates Pirlo and Inzaghi remarkably went the way of the latter. Benevento had not won in 11 games before this clash, losing six in that run to slump to just above the relegation zone, and Juventus should not have tripped up like this. Increasingly, the decision to appoint rookie coach Pirlo to coach Juventus is looking like sheer folly. They bossed the shot count 21-7 and had 73.4 per cent of possession, but a fourth league defeat of the season just about finishes off those 10-in-a-row hopes.
It's all gone Ron for Juve, but don't blame CR7
Ronaldo has scored just once from outside the penalty area in Serie A this season, and three times in all competitions. Now much more of a penalty-box predator, it felt like a throwback moment when he raided in from the right and unleashed the long-range blast that Montipo just about saw coming and pushed aside. In his 60-goal season for Real Madrid in 2011-12, Ronaldo scored 10 goals from outside the 18-yard box, a career-high. He had nine shots in all in this game, four of them on target, plus a disallowed goal. Some say he is not pulling his weight, but this defeat was not really his fault.
Arthur carries the can
Benevento were nuisances at times, but they barely carved out a decent chance across the 90 minutes. Luckily for them, a helping hand arrived when Arthur's stray pass found Gaich and the striker gobbled up the big chance. It was simply dire from the former Barcelona player, who was fed the ball from a throw-in and had time to pick his pass but ridiculously failed to spot the lurking Benevento man and fed the ball into his path. No wonder Arthur was substituted just a couple of minutes later.
Key Opta Facts:
- Benevento are the first newly promoted side to stay unbeaten in both league matches in Serie A v Juventus since Sampdoria in 2012-13.
- Juventus have lost a home Serie A game against a newly promoted side for the first time since January 2013 v Sampdoria.
- Benevento have won their first Serie A match against a team in the top-three positions of the table at the beginning of the matchday, after seven encounters lost and one draw.
Torino away on April 3 will be the first assignment for Juventus after the international break. Benevento will resume against Parma on the same date.