Arbeloa made his debut for Real in 2004 and revealed to liverpoolfc.tv: "I came on against Betis in the second half for 30 minutes.
"I played very well. It was a good game. We were losing 1-0 and the game ended up 1-1 thanks to Ronaldo's equaliser. I played full-back even though in Castilla I was playing in the centre.
"Of course, we had all of these great players playing for the club, but I didn't really think about that because I had to focus on my own game and make sure I did well.
"Afterwards, when I thought about it, I couldn't believe it.
"Then when I didn't play in the next game I began to think about all the players that had been at Castilla and made it through and become regulars at Real – there weren't many.
"Only two players from the Castilla team that I played for managed to make any kind of impression in the first team.
"They were Francisco Pavon and Alvaro Mejia and they have since left as well. I stayed there for another 18 months but in the end there was no option for me but to leave."