Marcus Rashford's free-kick and Ferran Torres's clinical finish in a dominant opening 20 minutes settled the match before it had properly started. Thibaut Courtois made several important saves to limit the damage, with the score remaining 2-0 at full-time. The last time La Liga was decided by a home Clásico was the 1931/32 season.
Arbeloa addressed the media in the Camp Nou press room with a composure that belied the magnitude of the moment.
On a Jude Bellingham elbow incident he felt should have been a red card: "To me it seemed clear there was an elbow — but I want to congratulate Barcelona for winning La Liga today."
On Kylian Mbappé, who did not travel due to a hamstring strain: "There are two weeks to go and we will have to see how his discomfort evolves to see whether he can play or not."
On whether he would have preferred Mbappé to have made the trip despite his injury: "I would have liked him to have been at 100 per cent and able to play from the beginning."
He acknowledged the pain the result would cause the club's supporters while trying to find something solid to build on.
"We cannot say many things because we understand the frustration and the disenchantment. We can only look to the future and learn what we have done wrong this year. We always get back up — and I understand the anger of the Real Madrid fan."
On the task that remains in the final three matches of the season: "Our season has effectively ended today but we cannot give up. We defend something much bigger than all of us — the badge of Madrid. We have to show that we are truly hurting."
On the wider question of what Real Madrid must do to rebuild: "That is not for me to analyse, but collectively we need to take a step forward and have a clear idea of what we need to do. For me that is the starting point — and learning from the fact that we have dropped many points we should not have. You can lose to Barcelona, but not to others."
On his own future at the club, Arbeloa was measured. A conversation with the club is expected.
"You know we will probably have a conversation with the club, as is normal. But I want the team to finish well and not let themselves drift in these final three matches. Finishing the season on the pitch — giving minutes to players who have not had them — is where I will put my focus."