Arsenal have revealed that youngster Ainsley Maitland-Niles is to miss between six and eight weeks with a fractured leg.
The 20-year-old sustained the injury during the early stages of the Gunners' 2-0 loss at the hands of Manchester City on the opening day of the Premier League season.
Maitland-Niles was filling in at left-back in the absence of Sead Kolasinac and Nacho Monreal, but Arsenal will at least have the latter back in their squad to face Chelsea this weekend.
Monreal and Danny Welbeck have both returned to full training ahead of Saturday evening's trip to Stamford Bridge.
Out-of-favour defender Carl Jenkinson has sprained his right ankle and will also miss up to two months of action, meanwhile, and Kolasinac is due to return to training in October.
Club captain Laurent Koscielny is Arsenal's other notable absentee, with the Frenchman still more than two months away from a return to training after damaging his Achilles tendon towards the end of last season.