Bayern won 4-3 on the night - and the quarterfinal 6-4 on aggregate. The flashpoint was Eduardo Camavinga being sent off for two yellow cards, with his second for stopping Bayern from taking a quick free-kick.
Arbeloa said afterwards: “It’s an action that no one understands how you can send a player off for something like that in a match of this nature. It's clear that the tie ended at that moment, and it is something totally inexplicable and unfair.
"We are very hurt because the tie slipped away from us in a way that we couldn’t control, and I feel very sorry for my players and the effort they have made.”
Arda Guler was also sent off after turning on referee Slavko Vincic following the final whistle.
Arbeloa continued: “I feel very proud of them, of the fans, of all those who traveled, of those at home, and of the club. If there’s one thing that hurts about this defeat, it's that we won’t win the Sixteenth this year, and above all, the way it happened.
“They are very hurt, especially because of the way it happened. From here, I also want to congratulate Bayern Munich on the great tie they played. But we would have liked them to beat us in a different way than how it happened, with an inexplicable sending-off that no one understands.
"And I think that’s why there is this sense of injustice, anger, and pain my players feel, seeing how their work, effort, and sacrifice on the field were undone by an action like the one the referee made.”
On Camavinga's second tellow card, Real's coach also insisted: “I think he issued the card precisely because of that, because Bayern players had to go and tell him it was the second yellow. I think referees often either don’t play football or don’t understand how to handle this type of situation.
"But beyond not knowing, I think it’s even worse not knowing that a player who had already received a card not long ago—because Camavinga came on in the second half—is being penalised. I think it’s a double mistake.”