Mikel Arteta said he is "worried" about the fitness of Arsenal defender William Saliba after the France international added to the club's growing injury list by lasting just five minutes of Sunday's 1-0 defeat against Liverpool at Anfield.
Dominik Szoboszlai's stunning 83rd minute free-kick -- described by Arteta as a "moment of magic" -- won the game for Liverpool and moved the champions two points clear at the top of the Premier League table.
Arsenal responded well to the loss of Saliba and controlled the game without creating clear chances, but Arteta's side now face an anxious wait on the 24-year-old, especially with Bukayo Saka and Kai Havertz already sidelined due to injury.
"He [Saliba] twisted his ankle during the warm-up," Arteta told reporters. "He came in and believed he could carry on, but from his first two actions you could see he couldn't cope, so we took him out.
"We had to put [Cristhian] Mosquera on and it was a big test for him at Anfield, but he had a great debut."
When asked if he was concerned about the extent of Saliba's injury, Arteta admitted he was worried about the loss of his centre-back.
"I am worried," he said. "When he cannot play in a game of that stature, there is clearly something wrong"
Arsenal's defeat at Anfield ended their 100% winning start to the season, but Arteta's side showed solidity and organisation before Szoboszlai's late winner.
There were signs of progress from Arteta's team, but he admitted that Arsenal need to learn how to win the biggest games.
"You cannot dominate here for 90 minutes, it is impossible," Arteta said. "At the end of the game, I said we have to find a way to win these big matches.
"You have to put the ball in the back of the net when you have it. We were much better than last year, much better, but we have to put the ball in the back of the net if you want to win the game.
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"I am very disappointed with the result, but I'm very proud of my players. There was nothing between the two teams. It was going to be decided by an individual error or a moment of magic.
"You have to take a lot of positives from the game. I haven't seen Liverpool at home suffering like they did against us."
Meanwhile, Arsenal goalkeeper David Raya said that the Premier League's new Puma ball is taking some adapting to but the change is the same for everyone this season.
"It's different to the Nike ball so we have to adapt to it. The grip is different, the kick is different," Raya said. "We just have to adapt after playing with the Nike ball for many years. It's the same for everybody.
"We showed a lot of character to keep Liverpool quiet. You have to take the positives from it. It's fine margins and a magical moment from them.
"We haven't been beaten from the top six clubs in many games. There are a lot of steps forward to take and learn in every single aspect. There's always things you have to learn."