Barcelona have brushed off the absence of leading striker Robert Lewandowski to win 1-0 at Atletico Madrid and open up a three-point lead at the top of La Liga.
Ousmane Dembele scored the deciding goal in the first half, netting with a low shot from close range after a pass from Gavi Paez in the 22nd minute.
Barca's main rivals for the Spanish title, Real Madrid, lost 2-1 at Villarreal on Saturday - only their second league defeat of the season.
"We knew it was going to be tough to win here, but after Madrid lost points against Villarreal we had to take advantage of the opportunity," Barcelona captain Sergio Busquets said.
"We have to keep adding points at the top."
Barcelona were without Lewandowski, the league's leading scorer with 13 goals, as the Poland striker serves out a three-game suspension from before the World Cup break.
He had faced Espanyol late last year after the suspension was temporarily lifted, but it got reinstated this week to keep him from playing.
Forward Antoine Griezmann had a couple of good opportunities to equalise for Atletico but could not capitalise on them at the Metropolitano stadium in the Spanish capital.
"We played well for most of the match," Atletico goalkeeper Jan Oblak said.
"We created chances but we were a bit unlucky. We could have scored a few times, but the ball just didn't go in."
Barcelona will now travel to Saudi Arabia to play in the Spanish Super Cup along with Real Madrid, Real Betis and Valencia.
The Catalan club take on Copa del Rey holders Betis on Thursday in one of the semi-finals, while Real Madrid and Valencia contest the other on Wednesday.
Real Sociedad continued their good run by winning 2-0 at Almeria to stay in third place.
David Silva and Alexander Sorloth scored a goal each early in the second half to give Sociedad their sixth victory in a row in all competitions.
Real Betis won 2-1 at Rayo Vallecano to end a three-game winless streak in the league and stay four points behind Sociedad in fourth place.
Sevilla beat Getafe 2-1 at home to end a six-game winless run in the league and edge out of the relegation zone on goal difference.
It was their first win since beating Mallorca 1-0 in October.