Italian champions Juventus suffered their first defeat of the season with a 3-1 loss against Lazio in Rome blowing open the Serie A title race.
Maurizio Sarri's eight-time reigning league champions remain second in the table, two points behind leaders Inter Milan after 15 matches.
Third-placed Lazio clawed to within just three points of Juventus after their first win at home against the Turin giants since December 2003.
Cristiano Ronaldo put Juventus ahead at the Stadio Olimpico when he picked up a Rodrigo Bentancur cross to tap in after 25 minutes.
But Luiz Felipe hit back for the Romans in front of 60,000 fans, nodding in just before the break.
Juan Cuadrado's sending off for a foul on Manuel Lazzari after 69 minutes proved to be the turning point.
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Lazio took control as Sergej Milinkovic-Savic connected with a Luis Alberto assist to fire in a stunning goal.
Goalkeeper Thomas Strakosha denied Ronaldo's header on the line while Juventus counterpart Wojciech Szczesny atoned for bringing down Joaquin Correa by saving Serie A top scorer Ciro Immobile's resulting penalty.
Felipe Caicedo snatched the third goal five minutes into injury time as Lazio earned their seventh straight win, fuelling ambitions of challenging for a first Serie A title since 2000.
"Lazio for the Scudetto? Maybe, it depends on how much they will be able to continue this extraordinary moment," said Sarri, "let's say it will be a three-way fight." "The red card changed everything for us," he added.
Juventus had been the only team left in Europe's top leagues to remain unbeaten in all competitions this season.
"My lads did something extraordinary tonight," said Inzaghi.
"We are in an excellent period and we must be ambitious.
"I have always had faith in this team. Six weeks ago people said we weren't getting results, but I remained calm.
"We'll enjoy this for a few hours, but from Thursday must get right back on track and aim to stay in the Europa League."
- Napoli's winless run continues -
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"We need a spark and hopefully that can be next week in the Champions League."