United were only able to win two games in Group C, and their fate was sealed when Basel secured a 2-1 victory in the final game of the group stage to knock the Premier League holders out of the competition.
The 70-year-old’s side travel to the Netherlands on Thursday to face Dutch champions Ajax in the Europa League last 32, but Ferguson conceded United’s elimination from Europe’s elite club competition still hurts.
“It was a massive disappointment, because my feeling is that if we’d gone through, we would have gone on to the final,” he said.
“The problem was the home game against Basel. We ended up losing our concentration and though we managed to salvage a draw, it was a bad result.
“We dominated the return game, but didn’t score and when that happens you don’t deserve to win.