Ousmane Dembele thumped in a 90th-minute winner as Barcelona beat Real Valladolid 1-0 and cut Atletico Madrid's advantage at the top of LaLiga to a solitary point.
Ronald Koeman's resurgent side had won their previous five top-flight matches but were short of their best for much of the first half, with Kenan Kodro hitting the crossbar for Valladolid.
Lionel Messi and his teammates tried to crank through the gears in the second half but struggled to find a breakthrough, even after Oscar Plano was sent off 11 minutes from time for a cynical foul on Dembele.
The France winger would have the final word, swiping home on the volley after Ronald Araujo made a nuisance of himself on the end of Frenkie de Jong's cross - setting up next weekend's pivotal Clasico showdown perfectly.
Barcelona goalkeeper Marc-Andre ter Stegen was back in action for the first time since Germany's humiliating 2-1 defeat to North Macedonia and he was relieved to see Kodro's header cannon to safety off the bar.
Messi won a free-kick in the 15th minute and clipped wide but the visitors continued to acquit themselves well.
Roque Mesa grazed the top of the netting with a speculative strike before Barca let the playmaker run unchallenged for around 30 yards to blast over.
Barcelona belatedly found some rhythm before the interval and Pedri linked up nicely with Messi to fire in a rasping low drive that Jordi Masip tipped against the right post.
Koeman's front three were all involved before the hour – Messi releasing Dembele to draw a brilliant low stop from Masip, with Antoine Griezmann sending an improvised diving header wide on the rebound.
Jordi Alba survived appeals for a penalty after the ball flicked off his hand inside the Barca box and Plano sliced wide on another threatening break.
A yellow card would arguably have been sufficient for Plano's petulance and Valladolid buckled at the last in what felt like a huge moment in the title race.
What does it mean? Barca on the march at the right time
Koeman's side have now won 13 and drawn one of their 14 LaLiga games in 2021. Atletico, beaten 1-0 at Sevilla on Sunday, find their form heading in the opposite direction and if Barca can beat Real Madrid – Zinedine Zidane's men are two points behind them in third – then they will certainly carry the look of champions.
Masip comes out on top against Messi
Barcelona's near-failure to record a sixth consecutive LaLiga victory owed much to Masip. A product of La Masia, the keeper made nine saves and operated in assured fashion throughout the 90 minutes – countless hours facing down Messi on the training ground over more than a decade undoubtedly coming in handy. He will have been devastated to see Dembele's close-range effort skim off his boot and in, but should hold his head high.
Griezmann unable to continue goal rush
Griezmann had been enjoying arguably his most consistent run of form in a Barcelona shirt before the international break as he netted in the resounding wins over Huesca and Real Sociedad. Two goals in three outings for France followed but he was kept on the margins by an energetic Valladolid side.
Koeman replaced the forward in the 64th minute, by which time he had been booked and sent both his attempts on goal off target.
Valladolid host Europa League quarter-finalists Granada on Sunday, a day on from Barcelona's vital Clasico encounter in the Spanish capital.