Arsenal have significant concerns over William Saliba's lower back injury at present.
The Gunners were initially hoping to have Saliba back within days or weeks when he went down.
However, his injury has not healed as they were expecting, per The Mail, which has led to concerns.
The club believe that structural damage to his back means that if he plays again this season, he may aggravate the issue and be out for much longer.
Wednesday's crucial clash at Manchester City in the Premier League was the hoped return date for Saliba.
However, it appears he will now be absent for the foreseeable future, dealing a huge blow to the club's title charge.