The Serie A side made the perfect start when Paz netted after just 118 seconds, and United were unable to respond, though they grabbed a goal back in second-half stoppage time through Joshua Zirkzee.
Fabregas, meanwhile, further underlined his credentials as one of Europe’s brightest young managers, but admitted he was not happy with himself for telling his players to conserve energy after Ramon’s fourth goal.
“I believe that tactically speaking the team played a rather good game,” he said.
“I regret maybe the last 10 minutes when I was the one telling the team to slow down the pace because there was another game and maybe with a 4-0 lead they could have managed something.
In the frame? Cesc Fabregas has been linked to Manchester United as a replacement for Michael Carrick
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“I told Tasos Douvikas not to run anymore, to stay in the middle and maybe that is what I regret, because I’m the first one who always pushes the fight until the end. That goal hurt me.”
Fabregas has been linked as a potential replacement for Carrick at Old Trafford, but he dismissed those questions ahead of the United game.
"I won't answer that question because I think that's not a very nice question," the former Arsenal, Chelsea and Barcelona midfielder said at his pre-match press conference on Tuesday.
"I don't think that shows enough respect to a great footballer and manager like Michael Carrick at the helm of a wonderful Manchester United side."
United now sit 20th in the Champions League table after their thrashing by Como, and Carrick went over to United’s 700-strong away support at the Stadio Giuseppe Sinigaglia - many of whom had already left - at full-time to apologise.
"It's a decision from the staff to not press man to man and sometimes leave space behind and try to get the ball, but sometimes when you give too much the ball to these teams, they get confidence," Fernandes said.
Asked about Fernandes’ comments in his post-match press conference, Carrick retorted sternly: "There's a little bit of whatever system you play, whatever tactics you play, if you don't run, and you don't run forward, and you don't run back, you aren't going to win."