Robert Lewandowski's brace snatched champions Barcelona a 2-1 win over lowly Celta Vigo to leave them third in La Liga, trailing leaders Real Madrid by seven points.

Xavi Hernandez's side needed a stoppage-time penalty converted by Lewandowski at the second attempt to find a way past a Celta Vigo side battling relegation, down in 17th place.

Lewandowski slammed the visitors ahead at Balaidos before half-time but Iago Aspas levelled for Rafa Benitez's Celta early in the second half.

Barcelona tamely struggled to find a way through before being gifted a late spot-kick for a clumsy foul on Lamine Yamal, which Lewandowski dispatched for his 12th goal of the season.

The Catalans are unbeaten in four matches since Xavi said he would depart at the end of the season and face Napoli on Wednesday in the Champions League last 16, with Europe the club's last realistic chance of silverware this season.

Xavi handed Brazilian forward Vitor Roque his first start for the club on the left of the attack, alongside Lewandowski and 16-year-old sensation Yamal.

The latter was Barcelona's brightest player once again, with the Catalans dependent on his skill and speed on the right flank to create danger.

Despite controlling the first half Barcelona failed to threaten much beyond a Yamal shot which Vicente Guaita did well to tip away.

At the other end Ronald Araujo sprinted back well to stop Jorgen Strand Larsen running through on goal.

Barca broke the deadlock in the 45th minute when Yamal fed Lewandowski, who lashed home superbly from just inside the area.

The lead did not last long, with Aspas pouncing two minutes into the second half to level.

A slick move from Celta was finished by the veteran forward after former Barcelona defender Oscar Mingueza backheeled the ball into his path.

Aspas's strike bounced in off Jules Kounde, with the deflection taking the ball over the outstretched arm of Marc-Andre ter Stegen.

Guaita got his fingertips to a swirling Raphinha free-kick as Barcelona hunted for the winner without success, until Yamal won a penalty in stoppage time.

Celta's Fran Beltran accidentally kicked the winger when trying to clear the ball and Lewandowski converted from the spot to steal Barcelona three points.

Guaita saved Lewandowski's first attempt but was off his line and the veteran Polish striker stroked home clinically after being given a reprieve.

Celta sit three points above the relegation zone after Cadiz, 18th, lost at Osasuna earlier on.

On Sunday league leaders Real Madrid can stretch their advantage when they visit Rayo Vallecano, currently five points clear of second-place Girona, who lead Barca by two.