Massimiliano Allegri called his Juventus side "sluggish and complacent" after they let a one-goal lead slip in a 2-1 defeat to Inter at San Siro.
The Bianconeri looked set to make it four wins from four Serie A matches when Stephan Lichtsteiner opened the scoring after 66 minutes, but the lead was quickly overturned by a determined Inter side.
Goals from Mauro Icardi and Ivan Perisic condemned Juventus to their first Serie A defeat to Inter since November 2012, and Allegri said he hoped his players would learn from the shock result.
"After taking the lead, we didn't even hold it for two minutes," Allegri told Sky Sport Italy.
"We got sluggish and complacent, dropping the intensity levels. This defeat has to burn within us and teach us a real lesson, getting our feet back on the ground.
"It was a dirty game, rough and a real battle. We needed more determination and hunger to bring home the result, especially once we had gone in front."
Allegri opted to leave Juventus' record signing Gonzalo Higuain out of his starting line-up, favouring Mario Mandzukic, and also played Miralem Pjanic as a deep-lying playmaker, in place of Mario Lemina.
Neither change seemed to have a positive impact but Allegri defended the decisions, saying: "I think Pjanic had an intelligent game in front of the defence.
"Lemina did well for a few games, but don't forget he only played nine times last season, so we can't put too much pressure on him.
"The real problem today is that Juventus were bad on a technical level - we gave the ball away cheaply, misplaced passes and above all conceded our third goal of the season on a corner.
"It's not easy for strikers when the whole team is playing badly. We need to relax, start preparing for the Cagliari game and put together a run of good results.
He added: "It's not a tragedy. I was worried we'd have such a strong series of early fixtures, but the lads largely did well.
"I think every now and then a defeat like this can do us good, if we are smart and humble enough to learn from it."