The France international was making his comeback from an Achilles injury he sustained at the end of last season
Laurent Koscielny could be facing another lengthy spell on the sidelines.
The 33-year-old limped off before the end of Arsenal’s Checkatrade Trophy win against Portsmouth at Fratton Park on Tuesday evening.
With around ten minutes to go the French defender signalled that he was feeling some discomfort and the physio jogged on.
The Gunners skipper played 45 minutes for the Under-21 side as they were duly smashed 5-0 by Derby County last week.
It was supposed to be the France international’s comeback from a seven-month lay-off from the Achilles injury he sustained during the Europa League semi-final defeat to Atletico Madrid.
The unfortunate injury meant the veteran centre-half missed France’s World Cup win in Russia.
Unai Emery previously hinted last week the French star is close to making his highly anticipated return to the senior squad.
He said: “He is looking well, with good performance, good feeling and I think he, today, is close to also playing with us.”
The Gunners have managed to cope without their captain, having gone on a 17-game unbeaten run in all competitions.
But his return to first-team action may have been hit with another injury blow.