The two teams have had contrasting fortunes in La Liga so far this season.
Leaders Barca boast a 100% record and are already eight points better off than defending champions Madrid after six matches.
However, Mourinho's men have shown signs of turning a corner recently, not least with a 4-1 rout of Ajax in the Champions League in midweek.
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And the Portuguese coach admits their league ambitions far outweigh those of simply beating their bitter rivals at the Nou Camp.
"Real Madrid-Barca is a match that we love to play. They probably do too," he told American channel beIN Sport TV.
"That means that a Clasico is a little more than other normal league matches. Football lovers all over the world stop when Barcelona play against Real Madrid.
"The number of viewers for the last Spanish Supercopa showed that there was more interest than for many Champions League matches.
"But our goal is to win the championship. El Clasico is only worth three points.
"This Sunday's match is a league match - two direct rivals who know that if one of them takes the three points the other can't."
Barca midfielder Sergio Busquets, meanwhile, is aware of the danger among Madrid's team as they look to make amends for their pre-season Supercopa defeat.
"Iker Casillas is one of the best goalkeepers in the world and has had a phenomenal career," he said.
"Sergio Ramos has great qualities and will play wherever you play, with or without the ball. And he's a great marker.
"Pepe is a key player and very powerful, Xabi Alonso is the one who directs and manages Madrid's game. His long balls behind the opponents' defence are dangerous and create a lot for Madrid.
"Mesut Ozil is a quality player with a great final pass, Karim Benzema also has a lot of quality in addition to goals and then there is Cristiano Ronaldo. He's a fantastic player, very powerful.
"We have to try to stay one step ahead of him, it will not be easy.
"All in all, they're a great team, great players and we have to be at our best."
Barca will be without captain Carles Puyol after he suffered a dislocated elbow during Tuesday's 2-0 Champions League win over Benfica, while centre-back partner Gerard Pique has not played in a fortnight because of a foot injury although he did return to training on Saturday.
Mourinho, meanwhile, should be able to select near enough his strongest team, with Kaka pushing for a starting berth after some impressive recent displays.