Thierry Henry and Zlatan Ibrahimovic scored in the second half as Barcelona squeezed past bottom club Xerez 2-0 to go five points clear at the top of La Liga on Wednesday.
This match had been brought forward two weeks because of Barcelona's participation in the Club World Cup, which starts in Abu Dhabi on Dec 9.
The unbeaten champions moved onto 33 points having played one game more than second-placed Real Madrid, on 28.
Barca sent out a weakened team with Ballon d'Or winner Lionel Messi and Ibrahimovic, who scored Sunday's winner in the 'clasico', on the bench and it showed in a forgettable first period.
But Pep Guardiola's halftime talk appeared to have an effect and two minutes after the re-start, full back Maxwell found space on the left and crossed for Henry to flick a header into the roof of the net.
Messi came off the bench to supply fellow substitute Ibrahimovic for the second goal in the final minute, as the Swedish striker lobbed Renan for his ninth of the campaign.