Just as it looked like Barcelona were going to follow up the Clasico with more frustration, a Lionel Messi spot-kick saw off Real Sociedad.
Lionel Messi scored a late penalty as Barcelona shook off a post-Clasico hangover and edged to a 1-0 win over Real Sociedad at Camp Nou.
Having lost first place in their defeat to rivals Real Madrid at Santiago Bernabeu six days ago, Barca took the chance to return to the summit, albeit in an unconvincing Camp Nou victory on Saturday.
Messi came into the contest having failed to score in six of his last seven games but he converted the crucial spot-kick with nine minutes remaining after a VAR review adjudged Robin Le Normand had handled a left-wing cross.
Madrid now trail by two points but have the chance to reclaim LaLiga top spot in Sunday's match against Barca head coach Quique Setien's former club Real Betis.
Martin Braithwaite was twice denied by goalkeeper Alex Remiro early on, Messi having created both chances, while Alexander Isak headed way off target at the end of a neat Real move, with Marc-Andre ter Stegen rarely troubled in the opening period.
Remiro blocked a close-range Messi shot before the Argentina international sent another low effort narrowly wide, his frustration showing with a late challenge on Mikel Merino that earned him a booking.
It was Messi who continued to look the most likely for Barca and, early in the second half, he sent a curling strike wide, had a free-kick blocked then fired over as defenders bore down on him in three separate chances.
Remiro got down to impressively tip away an Ivan Rakitic drive, before Gerard Pique headed straight at him as the hosts upped the pressure.
While La Real began to threaten on the break, a goalless draw was looking likely before the Barca breakthrough finally arrived.
Remiro could not reach Messi's penalty despite diving the right way, with the visitors unhappy at the handball decision, their frustration not helped by suggestions Barca had been offside in the build-up.
The offside flag did go up in stoppage time against substitute Ansu Fati, denying Jordi Alba a clinching second goal after a slick move involving Messi.
What does it mean? Late win prevents alarming slump
Had Barca not made their late breakthrough, the post-match picture would have looked very different. Instead of putting the onus back on Madrid, Zinedine Zidane's side would have had the chance to move three points clear, while Barca would have been on an alarming three-game slump at a key stage of the season.
Mikel Oyarzabal, Isak and Nacho Monreal were all unable to test Ter Stegen with promising counter-attacks when the match was goalless late on. While Barca were the better side, Setien will be breathing a big sigh of relief.
Penalty could get Messi back on track
It is rare that Messi would ever go goalless in six out of seven games, but he produced a strong performance here to respond from a quiet Clasico outing and will hope this sets him up for a strong end to the season. As well as the winning penalty, he created a game-high three chances and racked up six shots.
Isak frustrates for La Real
La Real came into this game on a six-game winning streak that could have continued had they shown more ruthlessness in the final third. Isak was among their most culpable, failing to find the target from four attempts on goal. Overall, Ter Stegen only had one save to make.
Barca are away to Real Mallorca next Saturday, with the March 18 second leg of their Champions League tie against Napoli also on the horizon. La Real have a short turnaround before they are at Eibar on Tuesday.