Arsenal captain Martin Odegaard faces a lengthy spell on the sidelines after a scan showed “significant” damage to his ankle.
The midfielder suffered the injury on international duty with Norway and missed Sunday’s north London derby win at Tottenham.
Boss Mikel Arteta gave a gloomy update on Odegaard’s condition ahead of Thursday night’s Champions League clash with Atalanta in Italy.
“The scan showed some damage around the ligaments in the ankle so we are going to miss him,” said Arteta.
“It’s something quite significant so we are going to lose him for a while. Hopefully not months.”
Arteta can welcome Declan Rice back into his midfield after he was suspended at Spurs.
The Spaniard has urged his players to step up to the plate in their captain’s absence, starting with their Champions League opener in Bergamo.
“We have to show that,” added Arteta. “He’s our captain. One of our biggest players, one of our most consistent players in the last two or three seasons.
“Our identity is related to his way of playing and his way of behaving. We are going to have to deal with that.
“It’s a great test for the team of how capable we are to show maybe a different face and that other players and other options can be very effective.”
Bukayo Saka limped off at Spurs but Arteta had better news on the England forward.
“Yes he was able to train today, he completed most of the session and yet he is available,” he said.
Manchester City, who Arsenal travel to on Sunday in an early-season title showdown, played at home against Inter Milan on Wednesday night, while the Gunners will have a day less to recover from a testing trip to Italy.
“Is that a disadvantage? Hopefully not,” said Arteta. “Hopefully we have so much energy from what happened on Sunday as well. It was great. We are looking at the positives.”
The extra demands on players, given there are two more matches in the new Champions League format, was brought into sharp focus this week when City star Rodri claimed players could go on strike.
But Gunners midfielder Jorginho insisted: “This situation is how it is.
“If the games are there we will work so hard to be here and at this level and we dreamed to be here so if its this situation we need to play these games, we always try to do our best to deliver.”