"We don't know anything more," said Arteta.

"It was big enough not to allow him to continue to play the game and that's a worry for us."

Saka, 22, had started his side's past two games before being withdrawn with injury concerns - and is now a doubt for Sunday's crucial Premier League game with champions Manchester City at Emirates Stadium.

But asked whether he regretted picking Saka against Lens, Arsenal boss Arteta said: "No. It was a knock that he had the other day and he was perfectly fine.

"It was a backheel, an action that can produce that kind of injury. He tried to backheel a ball in the first half and felt something muscular. He felt uncomfortable to carry on so we had to take him off.

"He hasn't really missed games. We gave him a break against Brentford [in the Carabao Cup] last week and that was all."

England forward Saka has been an ever-present in Arsenal's side and has started 87 consecutive league games.

So much of the Gunners' attacking play goes through Saka that it was no surprise their tempo and energy significantly reduced against Lens following his departure and they slipped to a disappointing loss in Group B.

Arteta will not want to lose such a key figure for the visit of Pep Guardiola's City, who lead the Premier League by one point from Tottenham and Arsenal.

He added: "Let's see what the extent of it is. The last few were more knocks than anything else."