The champions restored their four-point lead on second-placed Real Madrid, who had temporarily closed the gap by beating Celta Vigo on Friday.

Yamal curled into the top corner after 68 minutes to split the sides at Athletic's San Mames stadium in a hard-fought clash.

Barca coach Hansi Flick rotated his side, with Tuesday's visit to face Newcastle in the Champions League last 16 looming.

As a result his team put in a disjointed first-half display, creating little and looking far from their free-flowing best.

"We're already seeing what Lamine can do -- he puts it right in the top corner and there's nothing the keeper can do," Barca midfielder Pedri told Movistar.

"He's very young and he's only going to get better.

"What he has to do is not settle, to keep going like this, keep working and enjoying himself out there on the pitch, because he gives us a lot."

Barca's Ferran Torres floundered up front, bereft of form in 2026, and Athletic had the marginally better openings of a forgettable first half.

Joao Cancelo hit the frame of his own goal early on and Selton Sanchez ran through on goal but Barcelona stopper Joan Garcia got down well to dispossess him.

Ernesto Valverde's side put the ball in Barcelona's net before the break but Inaki Williams had strayed offside before finishing and it was ruled out.

In the second half Barca wanted Alejandro Rego sent off for a foul on Dani Olmo, while Athletic players appealed for Pau Cubarsi to be dismissed for bringing down Williams, but the referee settled for a yellow card in both instances.

Garcia made a good save to deny Oihan Sancet early in the second half, in a rare clear opening as the two Copa del Rey semi-final losing sides continued to tussle fruitlessly.

Barcelona's teenage star Yamal had an unusually quiet first hour by his standards but eventually broke free of Athletic defender Adama Boiro's close attentions to break the deadlock.

Substitute Pedri found Yamal in space and as Boiro slipped the 18-year-old whipped the ball into the top corner, in off the post, for his 19th goal of the season across all competitions.

It was the one outstanding moment of quality in the match and enough to decide it.

"It's a very bad feeling, I think we were better, we didn't deserve to lose," said Athletic defender Dani Vivian.

"Today was a tough day against the hardest team in the league, and we saw how (well) the team did, it's a shame we didn't get the win."