The decisive moment came in the 43rd minute when Tasos Douvikas won a penalty, allowing Da Cunha to send Filip Stankovic the wrong way. Como had dominated possession but found Venezia difficult to break down, while the visitors were left frustrated after an earlier handball decision against Luis Milla was overturned following a VAR review.
Fabregas admitted the decision had initially looked like a penalty to him, but accepted the explanation he received.
"When I saw it, it seemed a clear penalty to me. But before coming here I asked whether it was a penalty or not. I was told it wasn't because Luis doesn't move his arm and tries to move it away. It seemed a penalty to me, we were lucky, but the professionals who understand more than me said it wasn't."
He was particularly pleased with the way his players protected their advantage.
"An absolutely fundamental victory, the most important of the 13 matches we have played. Winning in football today is incredibly difficult. Well done to the team, especially defensively.
"We conceded only one shot on target, in the 94th minute. Looking at their matches against other teams, they have had four or five chances to score. Today we gave them practically nothing."
The Como coach also highlighted the importance of adapting to a demanding schedule, with his team unable to prepare for matches in the same way as previous seasons.
"We cannot train or prepare for matches as we have done in recent years. This has to become our mentality. We need a working culture suited to the way we have to play, with matches every three or four days."
Venezia FC coach Davide Nicola felt his side had competed well but believed the disputed incident had affected the contest.
"The referee did well, but for me it was a penalty all day long. Perhaps you win or lose afterwards, perhaps the game would have flowed more freely. It is disappointing because you have to keep the players calm. They may feel you are not protecting them."
Nicola insisted his players must not lose sight of their longer-term development.
"We want to be effective defensively without giving up on going forward. If you don't accept risks, you haven't yet completed your journey. We must never lose sight of our path."
Como's fourth consecutive league victory lifted them to 23 points, while Venezia were left to reflect on a third successive defeat.