A knee injury will keep Barcelona goalkeeper Marc-André ter Stegen out of action for several months after he was stretchered off the pitch during Sunday’s 5-1 La Liga win over Villarreal, a source confirmed to ESPN.

Barça coach Hansi Flick confirmed that the injury appeared to be “serious and serious”, but added that he could not give a timeframe until he had undergone further tests.

Radio station RAC1 reported that ter Stegen, who was admitted to a hospital near Villarreal’s Estadio de la Cerámica, could be out for up to eight months, which would put him out of action for the rest of the season.

“It doesn’t look good for Marc,” Flick said on Spanish television after the game. “We have to wait for the exact diagnosis of the injury, but it’s true, it seems really serious.”

Ter Stegen, 32, collapsed to the ground following a corner at the end of the first half and it was immediately clear that he could not continue. He was replaced by Iñaki Peña.

The German international’s injury marred an otherwise good day for Barça, who scored five goals to win six of their six La Liga games this season and remain four points clear at the top of the table.

“This injury makes us sad,” Flick said in a press conference. “If you win 5-1 at Villarreal, the fans here in the stadium and the viewers in front of the television will have seen a fantastic game.”

“Villarreal also played with incredible speed and was dynamic in the game. With great goals from us, we are very happy with the 5-1, but in the end we are sad because I think the risk of injuries will be high, but we have to wait for information.”

Ter Stegen joins Barça’s long injury list, as Ronald Araújo, Andreas Christensen, Marc Bernal, Frenkie de Jong, Gavi, Fermín López and Dani Olmo are also currently unavailable.

Despite this, Barça have the best record in LaLiga, with Flick once again relying on young players at Villarreal, with Sergi Domínguez and Pablo Torre starting for the first time this season, and Gerard Martín also coming into the team at left-back.

“The bottom line is that the team has good character,” Flick praised Barça’s ability to overcome setbacks this season.

“I would say the attitude is incredibly good. I love it every day, the mix of high concentration and at the same time having fun playing football. That’s what we like.”

“We have to accept (the injuries). Marc today, it was an accident. It’s really tough, but we have enough players. I’m really proud of the team and how they played. Everyone who came in played fantastically. It was a big win for us.”

A brace from Robert Lewandowski – his fifth and sixth goals of the LaLiga season – gave Barça a 2-0 lead before Villarreal’s Ayoze Pérez reduced the deficit just before half-time.

The hosts pulled out all the stops in the second half. The second of three goals was disallowed for offside and hit the crossbar before Pablo Torre restored Barça’s two-goal lead. Torre also set up the first goal for Lewandowski.

Raphinha then scored twice to give Barça the three points, scoring the second after a great pass from Lamine Yamal after a Thierno Barry header had been disallowed for offside.

There were some awkward moments in the closing stages of the game when Yamal was subjected to some hard fouls due to the increasing frustration of the Villarreal players.

“We have to protect every player,” said Flick. “I didn’t see the situations so clearly, maybe I can say more when analyzing the game, but I don’t want to say too much about Lamine.”

“He’s doing great, he’s got a lot of quality, but so are the other players. Lewandowski and Raphinha with the goals today, our centre-backs, our midfield is really creative. We’re a team in defence and attack, a compact unit… a team that loves to play for each other.”