Ronald Araujo's header helped Barcelona extend their lead on Real Madrid at the top of La Liga to seven points with a tight 1-0 win over Rayo Vallecano on Sunday.
Alvaro Arbeloa's Real Madrid host Atletico Madrid, fourth, later on in a derby clash.
Araujo nodded home Joao Cancelo's corner after 24 minutes to secure the three points at Camp Nou but goalkeeper Joan Garcia's superb display played just as big a part in their victory.
Hansi Flick's side were caught snoozing in the opening stages but Garcia made a fine save to deny Carlos Martin from close range.
Called up by Luis de la Fuente to the Spanish national team, Garcia made several excellent saves to keep Rayo at bay, with the Madrid side dominant in the second half.
At the other end Raphinha was guilty of profligate finishing on numerous occasions. The winger scuffed wide after picking Pathe Ciss's pocket and charging through on goal.
A few minutes later Ciss appeared to bring down teenage star Lamine Yamal in the area but the Barcelona player's appeals were ignored by the referee.
Yamal's superb cross, with the outside of his boot, created another fine chance for Raphinha but the Brazilian's mis-hit effort was tipped over by Augusto Batalla.
The champions took the lead through Araujo's header from Joao Cancelo's corner midway through the first half.
Araujo has not featured much since taking a mental health break late last year, but came on as a substitute in Barca's 7-2 Champions League rout of Newcastle in midweek.
With Eric Garcia rested following a muscle overload, Flick started the Uruguayan at right-back and was rewarded with what proved to be the winner.
The Catalans came close to a second after the interval but Yamal dragged a low effort across the face of goal.
Rayo took control and started generating dangerous chances as they searched for an equaliser.
Joan Garcia denied Alvaro Garcia and then produced a spectacular save to push away Unai Lopez's header.
Pacha Espino should have pulled the visitors level but, after beating Barca's high defensive line and staying onside, curled over the bar.
Garcia pushed away a Jorge de Frutos drive before six minutes of stoppage time were added but Barca clung on to triumph.