Inzaghi admits the performance wasn't good enough.
“It was not a good performance, all we can do is roll our sleeves up and get back to work," the coach told Sky Sport Italia.
“It's a game that forces us to reflect, to realise that Serie A is a different level. We lacked determination and the responsibility for that can only be mine. We are a newly-promoted club and must learn to fight it out for every ball.
“I must find out what is wrong. I have no arguments today, Spezia deserved the victory and we congratulate them, but playing like that we probably would've lost against anyone. It was not dissimilar to our performance in Week 8 last season against Pescara.
“This is the first game we got completely wrong in terms of approach, so we've got to learn from it and be completely different with Fiorentina after the break for international duty."