Real Betis coach Manuel Pellegrini felt they never gave their best after defeat in the Europa League to Manchester United.
United's 1-0 win saw Betis eliminated in the round of 16 5-1 on aggregate.
Pellegrini said: "The two games leave a slightly bitter taste because in five minutes at Old Trafford everything slipped away from us. We had a chance for 2-1 and then in a few minutes we find ourselves 3-1 behind and come away from Old Trafford beaten 4-1.
"We had three or four chances and they took the first one they had. I'm pleased with the personality of the team and that we don't change our philosophy against an opponent of this stature.
"We feel the support of the public. It's impossible to not feel it in a stadium full of almost 55,000 supporters."