"It is very frustrating," said the Reds boss, who confirmed defender Andre Wisdom was substituted in the first half as a precaution with a knee problem.
"We were leading twice in the game and we missed a hatful of chances and then to concede like we did at the end at the end was very disappointing.
"We were in control of the game with a few minutes to go and that is for our learning. We are walking back in the 87th minute and it is a disappointing goal when you analyse it from every aspect. When you are winning at home you don't need to commit and leave yourselves isolated and that is something we will improve on.
"Young Boys have won home and away against Udinese and you can see the flexibility in their game is very good. We are disappointed when you get 2-1 up with three or four minutes to go you have to control the game better and show better game management.
"We have to do better than that but it is a point and we move on the next game in the tournament. We have to get a good result and match the result of Young Boys.
"We wanted to qualify tonight and that was the ambition but it wasn't to be.
"We have to move on as we have an important game on Sunday (against his former club Swansea) and we'll take the next Europa League game when it comes up."