Robert Lewandowski and Raphinha each scored twice as La Liga leaders Barcelona cruised to a 5-1 victory over Villarreal on Sunday, though the win was overshadowed by a potentially serious knee injury to goalkeeper Marc-Andre ter Stegen.

Atletico Madrid, in fourth place, were held to a 1-1 draw by city rivals Rayo Vallecano, with Conor Gallagher scoring his second goal for the Rojiblancos.

Barcelona’s perfect start to the season – six wins from six – was marred when Ter Stegen was stretchered off after an awkward landing while collecting a cross. Early signs indicate he could miss the rest of the season.

"I think it will be a huge injury; when he lay down on the field, you could see it directly," Barcelona coach Hansi Flick told DAZN.

Lewandowski scored Barcelona’s first two goals and later missed a penalty in an entertaining battle at Villarreal’s Estadio de la Cerámica.

Ayoze Perez pulled Villarreal back into the game shortly before halftime. The previously unbeaten hosts had two goals disallowed, while Pablo Torre and Raphinha’s strikes secured Barcelona's victory.

After second-place Real Madrid thrashed Espanyol 4-1 on Saturday, the Catalans restored their four-point lead over the defending champions.

"It's very important for us that we played a game away from home, scored five goals, and in the end, we have three points," Lewandowski said.

"In the end, it doesn't matter how we win, as long as we win, that's perfect."

Flick gave Eric Garcia another start in defensive midfield despite his early red card in the midweek Champions League defeat against Monaco.

The German coach also started reserve team players Gerard Martin and Sergi Dominguez, along with playmaker Torre, in place of the injured Dani Olmo.

Teenage star Lamine Yamal hit the post early on before Lewandowski slotted home in the 20th minute after Torre set him up.

Villarreal goalkeeper Diego Conde did well to keep out a bundled effort from Lewandowski, but the Polish striker pounced after 35 minutes for his second goal.

Conde saved Garcia’s header, but Lewandowski converted the rebound with an acrobatic finish from close range.

It was Lewandowski’s sixth La Liga goal of the season, putting him two clear of Real Madrid’s Kylian Mbappe in the race for Spain’s Golden Boot.

Villarreal frequently threatened on the counter, and Perez gave them a lifeline after Nicolas Pepe set him up.

Ter Stegen thwarted Pepe with a sensational one-on-one save before halftime, but the Barcelona captain was later stretchered off after catching a corner. He was replaced by Inaki Pena.

Pepe’s goal early in the second half was disallowed for a marginal offside call, and Yeremy Pino hit the bar with a header as Marcelino Garcia Toral's side pushed Barcelona back.

Torre extended Barcelona’s lead with a deflected strike from the edge of the box, a crucial blow given Villarreal’s momentum.

Lewandowski hit the post from the spot after Eric Bailly brought down Yamal, and Villarreal’s Thierno Barry had a goal ruled out for offside.

Raphinha ended any hopes of a Villarreal comeback, first with a deflected shot and then finishing after Yamal’s superb pass left him with only Conde to beat.

"(Ter Stegen) is a very special and important person in the dressing room. This victory is 100% for him," Raphinha told DAZN.

Real Madrid goalkeeper Thibaut Courtois sent Ter Stegen a message on social media platform X.

"It hurt me a lot to see you leave the pitch like that," the Belgian wrote. "I hope you can recover soon, and we see you back in goal."

In a Madrid derby, Diego Simeone's unbeaten Atletico could not find a way past Rayo Vallecano.

Rayo’s Isi Palazon scored from close range after 35 minutes, and the goal was eventually awarded after initially being ruled offside.

Gallagher finished neatly from the edge of the box early in the second half after Alexander Sorloth set him up.

"(At halftime Simeone) told us we all had to run; these days, anyone not running here cannot play," Atletico captain Koke told Movistar.

"We had chances to get the winner, but it wasn’t to be."

Athletic Bilbao overtook Atletico to move into third place with a 3-1 win against Celta Vigo.