Goals from Francesco Ruocco and Ismael Cajazzo in the closing stages sealed a stunning win for the Serie B side, sending the Biancocelesti crashing out of the competition and leaving head coach Gennaro Gattuso to face difficult questions after the final whistle.
Gattuso, speaking to Mediaset, did not shy away from the scale of the setback.
"Yes, it's a blow. I'll take responsibility because that's right, but now we keep quiet and get back to work. We accept the responsibility. But we knew, as I told you the other day too, that we still have a lot of work to do and we move forward. It's normal that it hurts right now, we need to apologise because, as you rightly said, this team played a final three months ago. We went out with what was effectively a Serie B side and we take responsibility for that.
"But we move forward, and certainly, alongside these lads, as I've said many times since I arrived, they're giving everything and it isn't enough. We definitely still have plenty of areas we need to improve."
Pressed on whether the defence and attack in particular needed reinforcement in the transfer market, Gattuso declined to be drawn.
"Today isn't about the transfer market. Today there were players out on the pitch, we're talking about the players who played. It's too easy to talk about the market: we're missing this, we're missing that. Today we take responsibility, we own it, and afterwards we'll see what we can do in the coming days."
Asked to assess the performance itself, despite the result, Gattuso pointed to a sluggish start as the key issue.
"For sure, for sure. But it stings. We have to be sharp, there's no such thing as an easy game. It's true we had some chances, but I think in the first half we did things by halves: they made us run backwards, we never managed to break lines, we never managed to be aggressive, we gave up ground. I think we need to improve on that. I'd rather the players have chances and miss them, because it means we're doing things the right way.
"Afterwards it's normal that, in this climate, playing like this... but we know it, I said from day one that we arrived that this can't be an excuse. We know well that we need to stick together, to work, because only through work, a sense of belonging, and the desire to have a good season — because otherwise it becomes difficult — only through work can we come through this."
Questioned on whether his squad remains united despite ongoing difficulties dating back to last season, Gattuso pushed back on any suggestion of division.
"No, believe me, they're working well. This is a group that wants to work. We've changed a lot: last season there was a master of the 4-3-3, they played by department. This year we want to do something different. We've been working for forty days: if it's better than me, in forty days it's difficult for them to have absorbed every concept. But there's real desire, real willingness, and I think that's important. This evening, as I said before, is a bitter pill, it's a real punch in the face and we felt it, and we hope we can be good enough to work with calm. Afterwards it's normal that people outside aren't happy, but we know it and we hope to change that dynamic too."
Mantova head coach Francesco Modesto struck a markedly different tone in his own press conference, careful to temper the celebrations even as his players savoured a famous night.
"No, naturally we're pleased because we knew what kind of opponent we'd be facing. There were difficult moments in the game, they had chances, but I liked the spirit of the team. This is the spirit we'll need to bring into Serie B, because it's going to be a long and difficult league season. I'm happy for the fans who followed us, for them it's an immense joy. But our league campaign is a different matter and it starts on Saturday, we'll need to be focused and understand that our attention has to be maximum right from the start."
Modesto also reflected on the challenge of fielding several players out of position against a side of Lazio's quality.
"Games like this give you a boost, playing here at the Olimpico against a team of Lazio's level, who reached the Coppa Italia final last season. We did well to sit in a low block, that's the attitude I carry with me. We need to improve on things we also saw today, and as for the lads I had to use in different roles out of necessity, the coach has to understand where he can use his players. They're so willing that they always give me everything, I have no issue with that at all. You know we need a bit of help to fill out the squad, we could use a hand there."
Asked to send a message to Gattuso, whom he faced across the touchline, Modesto spoke warmly of his counterpart.
"I have huge respect for Rino, as a person and as a coach, we're both from Calabria. He's made football history and he's still making it because he's a well-prepared coach, we said hello because we hadn't seen each other in a long time. Today I was fortunate — if we replay the match, they win it, because they had the chances. So many games are decided by moments, and they can lead you to important wins."
On whether his side had exceeded even the rosiest of expectations, Modesto was careful not to get carried away.
"I don't want to dampen the enthusiasm, but from tomorrow we need to think about other things. The win is good, but we have to focus on what we can do next. I was level with the second goal, and I could see the ball was onside."