Whilst there is no indication that Nacho Monreal is becoming any less dependable as a left-back - the 32 year old has been suffering the painful setback of a hamstring injury.
The ultimate question on the mind of Unai Emery is whether the physical Bosnian Sead Kolasinac is in solid contention to be Arsenal's starting left-back.
New boss, new perspective
Emery has been very effective in the transfer market during his brief period at Arsenal - the signings of Lucas Torreira and Bernd Leno have been sensational to this date and the Gunner faithful seem confident in placing the trust of the transfer market in Unai Emery.
Arsene Wenger signed Monreal in January 2013 as a competitor to Kieran Gibbs' first choice place in the side: six seasons on, Monreal is a reliable, solid starter for Arsenal, and Gibbs in contrast is stuck in the Championship at West Bromwich Albion.
Now it seems that the time has come for the experienced Spaniard and Arsenal need to look forward to new potential options.
Will Maitland-Niles finally get his chance?
Nacho Monreal moving on opens up a door of possibility for 21 year old academy graduate Ainsley Maitland-Niles to occupy the left-back role that he had been utilised in under the leadership of Gunner legend Wenger.
Using the youngster would undoubtedly the cheaper option - there would be no need to sign a left back and needless to say that Arsenal would have another home-grown English player in their registered squad.
Unfortunately for the talented Englishman, Unai Emery has shown a preference to use Stephan Lichtsteiner as a left-back should both Kolasinac and Monreal be unavailable - which seemingly takes another two seasons away from Maitland-Niles' chances of finding his way into the first team.
What do the fans want?
On the other hand Unai Emery could make a move on in demand wing-back Ferland Mendy from Olympique Lyonnais, the 23 year old Frenchman was extraordinary in both fixtures against Manchester City in the Champions League group stage.
Many Arsenal fans picked him out as a potential replacement for the Gunners star (talkSPORT).
The hot prospect from Ligue 1 is set to remain in Lyon until summer 2023, so the monetary demands from the French giants could be out of Arsenal's reach at this moment in time - with Emery having to cope with such a low budget in comparison to his Premier League rivals.
Back the Bosnian?
Of course, in the previous summer, Arsene Wenger signed Sead Kolasinac on a free transfer from FC Schalke 04, a great transfer at the time: yet it has now managed to leave the club in a slight predicament.
It is perceived by many that Sead Kolasinac is too good to be a backup left-back, in fact, he would be too good at any club as a backup.
However, it is up for debate as to whether the Bosnian is good enough to start for Arsenal, and considering his recent injury issues, whether he is a stable choice for Emery as a starter.