Real currently lead Barca on the Primera Liga table.
Former Liverpool fullback Arbeloa said: "Barcelona, since last year has played at a very high level. With this demand, when you suffer a little, there is talk of a slump or crisis, but I think this season they've played well.
"Against Stuttgart, they returned to their best.
"We're talking about one of the best teams in history, they're playing very well and you must admit it. For us it will be difficult to win the league against this team, but it motivates us more."