Arsenal should attempt to bring the 33-year-old back to North London.
Arsenal bowed out of the League Cup on Wednesday following a 2-0 defeat by Southampton at the Emirates Stadium.
Right-back Carl Jenkinson was the villain of the piece after his first-half error directly led to the Saints' second goal.
Manager Arsene Wenger has little choice but to persevere with Jenkinson for the moment by virtue of the fact that Hector Bellerin and Mathieu Debuchy are injured.
But the French boss needs to strengthen that position in January - and he might already know of a potential replacement.
Bacary Sagna is out of contract with Manchester City this summer and the 33-year-old - who quit Arsenal for City in 2014, after winning the FA Cup - confirmed to Bein Sports, via ESPN, this week that there is no negotiations over an extension.
With the right offer, City could be tempted to let him go in January rather than lose him for free next summer, if Pep Guardiola does not intend on keeping him.
Even at 33, the France international is far better than Jenkinson and Debuchy, and he is a figure who 21-year-old Bellerin could learn a lot from as he continues his development.
Despite joining the Sky Blues, he left the North London side on relatively good terms and Wenger may have him back.
Whether Sagna himself would rejoin Arsenal is another question, but he, like so many others who have left the club, never really rediscovered the form he showed under Wenger and it might be tempting for him.
Guardiola would not like to strengthen a Premier League title rival, with Arsenal two points behind his side, but a decent offer would give the club's hierarchy something to think about.