Barcelona captain Sergi Busquets admitted frustration after defeat at Manchester United.
The 2-1 loss sees Barca eliminated 4-3 on aggregate from the Europa League.
Busquets said, "We played well in the first half.
"We had a couple of chances to go 2-0 up. But in the second half, United were much better and the match changed. Even when the scoreline was against us we had opportunities to equalise and we kept on competing.
"Little details mean that we are out."