Just drew at the weekend. But they remain so strong at home. Missing the injured Arthur and Ousmane Dembele.
Barcelona's good run of form was halted by Real Sociedad on Saturday, as they could only draw 2-2 in that away fixture.
Their home form remains great, though. They have won every home LaLiga match they've played this season.
This is the rescheduled match that was due to be played in October, but cancelled because of political tension.
Starting midfielder Arthur Melo is out injured. Can be replaced by Ivan Rakitic, who is experienced and who was a starter last season.
Backup forward Ousmane Dembele is out injured.
Starting full-backs Nelson Semedo and Jordi Alba both returned from injury at the weekend. They didn't look 100 percent, but should be closer to match sharpness now.
Barcelona will have had one extra day of rest ahead of this match as they were last in action on Saturday and Real Madrid were in action on Sunday.
Coach Ernesto Valverde has admitted that he thinks it is a small advantage for Barcelona to have had one extra day to prepare.