Barcelona striker Robert Lewandowski ended his barren goalscoring spell with a brace to rescue the Spanish champions a 2-1 win over visiting Alaves in La Liga on Sunday.

Samu Omorodion sent the visitors ahead in the first minute against a dire Barcelona but Lewandowski's second half double rescued the hosts three points.

The victory keeps Barcelona in touching distance of shock leaders Girona, who are four points ahead, and second place Real Madrid, who have a two-point advantage, after both won Saturday.

Veteran forward Lewandowski scored a brilliant header early in the second half and thrashed home a penalty in the 77th minute to reach seven league goals.

Catalonia is in drought and Lewandowski was enduring one too, with the striker on his worst stretch of form for over a decade, having failed to score in six appearances prior.

Barcelona are also on their own miserable run of performances, which Xavi said is because the players are nervous, especially the younger ones, due to heavy criticism.

"We were more tense than normal because of all the noise generated around the team," Xavi told reporters after Barca's comeback.

"Situations are being created that are not real, and they affect (the players).

"It happened to me as a player and it's happening to my players."

Before the match Xavi said the team were not in crisis despite the recent Clasico defeat and a stumble against Shakhtar Donetsk in midweek, and that it was up to him to bring the team out of their slump.

The coach handed Pedri his first start after injury, deployed Joao Cancelo at left-back for the first time and brought 16-year-old starlet Lamine Yamal back into the side.

It took just 18 seconds for Alaves to strike.

Ilkay Gundogan lost the ball in midfield to Jon Guridi and with Barcelona's defence in total disarray, he fed Javi Lopez to cross for Omorodion, who slotted through Marc-Andre ter Stegen's legs.

"We cannot make those mistakes, it's unacceptable," said Xavi.

"We're giving far too much away and that takes a toll."

- Wasted chances -

Barcelona were easily pulled apart on multiple occasions on the first half, with Alaves target man Omorodion, only 19, bettering Jules Kounde on several occasions.

Xavi switched the French centre-back to right back midway through the first half, after the striker barged past Kounde and hit the crossbar.

Omorodion fired wide one-on-one with Ter Stegen on another occasion and Alaves could easily have walked off three goals up, but it was just one.

Lewandowski, 35 and at times in recent weeks looking it, was denied by Alaves goalkeeper Antonio Sivera -- the hosts' only chance of the first period.

Fans whistled Barca players off at the break, dismayed by another lifeless display. Barcelona reacted, levelling early in the second half.

Kounde crossed from the right and Lewandowski arced a brilliant header beyond Sivera's reach and into the net.

Xavi sent on Raphinha, Ferran Torres and Alejandro Balde, hoping their fresh legs would make the difference.

Yamal, booked for diving earlier on, stung Sivera's hands with a hard, low strike at the near post, with Barcelona finally playing with fluency.

Barcelona moved ahead when Torres was clumsily felled in the area by Abdel Abqar and Lewandowski smashed the penalty into the roof of the net to clinch the points.

"Sad, very sad," Alaves coach Luis Garcia summed up his team's defeat, that left them 15th, five points above the relegation zone. "The key is in the first half, if it's 2-0, or 3-0, it's a different story."

Xavi said he was convinced Barcelona would improve and tried to highlight the positives.

"We managed to get the win without playing well, that means we have a winning mentality, character, faith, (and) courage," he added.

"I was softer than ever (at half-time), the team needed affection."