Barca go into the game eight points clear of Real.
"Iker Casillas is one of the best goalkeepers in the world and has had a phenomenal career," Busquets 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.
"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."