Midfielder Ainsley Maitland-Niles has suffered a "small fracture" to his left leg and will be out for six to eight weeks, Arsenal have announced.
Maitland-Niles filled in at left-back in the 2-0 loss to City but limped off in the first half, and Arsenal said Thursday he has "a small fracture to his left fibula".
Carl Jenkinson is, however, expected to be out for six to eight weeks after he "sustained a significant sprain to his right ankle", Arsenal have confirmed.
Despite not being a natural left-back, Maitland-Niles did play their numerous times throughout last season, in particular in the Europa League, and new manager Unai Emery showed faith in him in that position once again on Sunday.
On long-term injury victims Sead Kolasinac and Laurent Koscielny, the news is broadly positive, with the defensive players expected to return to training in October and November respectively.
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The biggest headache for Virat Kohli to sort out the top order woes and he will have to juggle a bit with his batting options. But it still needed a robust effort from two of the side's senior batsmen to restore the dressing room's confidence.
Meanwhile, Arsenal have sent academy defender Krystian Bielik to League One side Charlton on loan for the season to gain more first-team experience.
The injury to Maitland-Niles was obvious but now, the club has confirmed the extent of the knock picked up by the 20-year-old.
Nacho Monreal also returned to training earlier this week and could be an option for Unai Emery at left-back against the Blues, depending on his fitness.
France global Laurent Koscielny, who missed his nation's World Cup-winning campaign with an Achilles tendon tear, is on the mend and is expected to return to training in November.