Madrid are already eight points behind the Catalans after a poor start to the season.
Barca, meanwhile, have taken maximum points from their opening six games, and Xavi is keen to increase the lead.
"It would be an important victory, to calm our nerves and leave our main rivals 11 points behind us," he said.
"It's a big opportunity but nothing is decisive. There is still plenty of life left in the league whatever happens.
"We will try to enjoy it and make the public enjoy it too. We are arriving in good shape, despite [Carles] Puyol's injury."
Puyol will miss the game after dislocating his elbow in Barcelona's midweek Champions League match.
The match between Barcelona and Real Madrid will take place at the Nou Camp on Sunday evening.