The weekend program features three big matches.
Ancelotti's Real settles accounts with the other surprise leaders, Pellegrini's Betis and Luiz Felipe, Roma's opponent in the Europa League.
Both have full points and Real have replaced Casemiro with Tchouameni.
Lewandowski hopes for yet another double by driving Barca home to a Seville in full crisis (two knockouts and an equal with modest opponents).
Kounde returns for the first time to the stage of its enhancement.
Simeone's Atletico, a little late, play at home with a tough nut to crack like Real Sociedad, focusing on the Morata-Joao Felix duo.
After two defeats, Gattuso's Valencia, who have just taken Kluivert, seek redemption by hosting Getafe.
The picture of the fourth day (RESULTS AND RANKINGS)
Celta Vigo-Cadiz 3-0
Mallorca-Girona at 2 pm
Real Madrid-Betis at 4.15 pm
Real Sociedad- Atletico Madrid at 6.30 pm
Seville-Barcelona at 9 pm
Osasuna-Vallecano Sunday at 2 pm
Athletic Bilbao-Espanyol at 4.15 pm
Villarreal-Elche at 6 pm
Valencia-Getafe 9 pm
Valladolid-Almeria Monday 9 pm