Roger Schmidt admitted he will never be able to forget the disappointment of Bayer Leverkusen's failure to qualify for the knockout stages of the Champions League.
The German club ended up missing out on second place in Group E due to their inferior head-to-head record with Roma, who join Barcelona in going through to the last 16.
Leverkusen needed to better the Italian side's result against BATE to go through, but both sides drew their final match to finish on six points.
Schmidt's side - who peppered Barcelona's goal in the second half but were unable to find a winner - are left to accept the consolation prize of a place in the Europa League.
"I can't believe it, I am very disappointed we did not win this match. Roma not winning against Borisov on top of that is even more bitter," Schmidt told Sky.
"The way this group stage went for us with all these missed chances and the bad luck we had is very hard.
"This disappointment will last with me forever, I will not forget it."
Lionel Messi opened the scoring for Barca before Javier Hernandez responded, but the hosts in Germany were unable to find a winner.
