Allegri is demanding a response after the 2-1 reverse.
“After taking the lead, we didn't even hold it for two minutes," Allegri told Sky Sport Italia.
“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 added: “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.
“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."