By ESPNSTAR.com staff
The Catalan side expectedly dominated possession against Neil Lennon's Celtic, but were undone by a Victor Wanyama header midway through the first half, before 18-year old Tony Watt finished an 83rd minute counter attack to pull off a memorable upset.
Although Barcelona playmaker Lionel Messi managed to score a late consolation, Fabregas told the club's official website that the team should have done better with the opportunities they created throughout the game.
"There is no such thing as injustice or justice in football. You have to win and that’s it," he said.
"We lacked depth. We had our chances, but failed to convert them, whereas they scored with the few chances they had."
Despite the loss, Tito Vilanova's side retained top spot in Group G, and Fabregas is confident the team remain on course to qualify for the next round.
"We are very pleased with the season that we are having so far, and we have to stick to our style of play and our own philosophy," he stated.
"We have two games left in the group stage and we will try to win them."
Barcelona return to La Liga action this weekend with a fixture away to Mallorca.