Como had built a four-goal lead before Joshua Zirkzee scored a late consolation for Michael Carrick’s side. Nico Paz scored twice and supplied an assist, while Tasos Douvikas and Jacobo Ramon also found the net in a landmark European result for the Italian club.
Fabregas said the decision to reduce the intensity had been his, and he regretted allowing United a way back into the game.
“I regret the last 10 minutes because I was the one who told the team to slow down the tempo because there's another match and at 4-0 we could manage things a little,” he said.
“I told the players to stop running and stay in the middle and that is something I regret because I'm the first to always push them to fight until the end. Their goal hurt me because we dropped our intensity and dropped our defensive block, but it was my fault.”
The Como coach was nevertheless delighted with how his players carried out the approach they had worked on in training. He highlighted their pressing and the conviction with which they played against a club with a far greater European history.
“I'm very happy with how the players applied everything we tried to do, not only in terms of quality, which was high, but also the way we were pressing relentlessly until the 85th minute,” Fabregas said.
“We are trying to create a culture at the club, a style of play and an identity. Tonight was another convincing moment for us.”
The victory carried particular meaning for a club that were playing in Italy’s fourth tier only seven years ago. Fabregas said he hoped the result would give supporters, including young fans, a reason to feel proud of their team.
“I can't lie to you that it (beating United) wasn't pride,” he said. “We know the history of our club, how much they have suffered over the last many years. Obviously, I hope that tomorrow all the boys and girls go to school wearing the Como shirt and feel proud.”
Fabregas also praised the players for delivering the style of football he wants Como to develop, rather than focusing solely on the scoreline.
“I always tell the lads, enjoy yourselves, fight, do everything to make the best career possible for each one of you, because it goes by quickly,” he said.
“They made me enjoy myself tonight, but not so much for the win, for the result, because they played like I like my team to play, with conviction, with quality, with a clear head, with aggressiveness, with a fierce pressing.”
Paz, whose two goals helped dismantle Manchester United’s defence, described the occasion as one he would remember for the rest of his career.
“It has been one of the most beautiful nights of my career,” he said. “I'm still young, but I will never forget it. I used to dream of playing in a match like this, and tonight we've gone even further. It's a historic night for Como fans.”