Juventus captain Gianluigi Buffon lamented the fact his side were unable to hang on to their lead in the 2-1 loss against arch-rivals Inter Milan on Sunday.
The reigning Serie A champions took the lead in the 66th minute courtesy of an effort by Stephan Lichtsteiner, but goals from Mauro Icardi and Ivan Perisic condemned Massimiliano Allegri's side to their first league defeat since October 2015.
"It hurts, because for 65 minutes we played badly and weren't very sharp in our passing, but we still went in front," he told Sky Sport Italia.
"A side like ours cannot and must not lose from that situation. A draw can happen, but not a defeat. You take these results home with something other than tactics and fluidity. You need determination and grit," he said.
Despite being disappointed by the loss, the veteran shot-stopper believes it could be a good thing to help them avoid becoming complacent in future.
"I think this defeat will do us good and it's perhaps normal not to be at 1,000 percent hunger this early in the season," he explained.
"We were put under pressure on the pitch and need to improve things. This is the third goal of the season we've let in from a corner and that's really not like us.
"Aside from what the media says about our strength, which could well be true, we have to prove it on the pitch in every single game."
Allegri's side will look to bounce back from their defeat when they host Cagliari in on Wednesday.