Louis van Gaal accepted it was "very disappointing" for Manchester United to exit the Europa League to rivals Liverpool, but said his side had enough chances to progress to the quarter-finals.
Liverpool went through 3-1 on aggregate despite falling behind on the night to Anthony Martial's penalty.
David de Gea made a series of stunning saves to keep United in the match, but he was left helpless when Philippe Coutinho beat Guillermo Varela before lifting home a sumptuous finish as the match ended 1-1 at Old Trafford on Thursday.
"Very disappointing because we could have the chance, that is the feeling in the dressing room," Van Gaal told BT Sport.
"We have created enough chances and we know of course when you are attacking in this way that also Liverpool has counter chances, but the way that we conceded that goal, at half-time they were all so disappointed.
"If we don't concede that goal I think it was possible. I was very pleased that the fans are seeing everything and applauded after.
"We have tried to do everything, also in the second half we had chances, Fellaini with his head and his foot but then you have to score three goals and that's not too easy.
"But we have fought til the end. If we did not concede that goal in the last seconds of the first half, it was critical."
Van Gaal refused to blame Varela or De Gea for Liverpool's goal, preferring to praise Coutinho for an inspired run and finish.
"You have to give also credit to Coutinho, it was a fantastic action," he said.
"You can also say that we have had fantastic actions but you need also a little bit of luck, but when you say that too much as a manager it's not good."
United now face a Premier League clash against Manchester City on Sunday, with both sides gunning for the fourth and final Champions League qualification place.
"That's the schedule we have and we have to cope with it," Van Gaal said.
"They have given everything and more than everything I think and still we have to play against Manchester City and they have one more day to recover but it was the same against Arsenal and we beat Arsenal."