Goals from Martin Baturina, Tasos Douvikas, Assane Diao and Maximo Perrone gave Como a statement win on their debut in the competition at the Stadio Sinigaglia, with Andrija Maksimovic's reply for RB Leipzig doing little to trouble the hosts.
The two coaches offered starkly different reflections afterwards, one built on quiet satisfaction and the other on candid self-criticism.
"It's always important to start a competition with three points, whether it's the Champions League or any other competition. For us this is a reward for the great work the team did last year, and we're very happy to be part of it," Fabregas said.
"But we can't forget who we are. We have to stay humble and keep our feet on the ground."
Speaking later in his press conference, the Como head coach turned his attention quickly to what comes next.
"I'm obviously happy, when you win I always am. Now I have the responsibility of getting the team thinking about Monday's match against Parma, and the fact that the league now comes before everything," he said. "It was a historic night for the club and for the people, one they'll still be talking about in ten years. This is the beauty of football, and I hope the fans enjoyed it as much as we did. In five minutes, though, we'll have to start thinking about Parma."
Fabregas was also pleased with how his side managed the contest tactically.
"I'm pleased with how we read the match at every stage, and that matters in a competition where there are plenty of teams stronger than you," he said. "We knew when to be aggressive and when to defend, and we understood the Champions League level when we went from almost making it 4-0 to it being 3-1.
"We covered well with a deeper line in the second half and still had several chances to score."
He added that Como had prepared specifically for Leipzig's approach: "We knew Leipzig would press us aggressively, so we tried to analyse their game, study their positioning and understand what they'd do against us."
He also had a message for one absentee: "I dedicate this win to Caqueret. We all rate him highly, and we recognise that leaving him off the Champions League list was down to squad numbers, not a lack of merit."
Demichelis, for his part, had no interest in dressing up the result.
"It was a difficult match. I think we defended very poorly," the Argentine said. "We had studied how they move, how they rotate and how they manage their positions, but in many phases of the match we defended badly without the ball." He was equally blunt about his side's struggles in possession: "We weren't able to manage the ball well enough to create more threats."
Pressed on whether Como's quality had caught Leipzig off guard, Demichelis pointed instead to the gulf in continuity between the two squads.
"Did their quality and intensity surprise me? No. I don't think that was the difference," he said. "Como is a team that rotates very well and has had the same identity for three years. We've only just started building our style of play, with a lot of players who arrived at the end of the transfer window and have only been working together for a week or ten days. We'll keep working and we'll improve."
He identified the moment Como made it 3-0 as the turning point: "We started the second half very well, moving the ball and pushing them back into their own half, but just when we were at our best, they scored on their first attack of the half. That was a very significant emotional blow."