Lack of a quality replacement
Whilst it might be easy to say that Sagna is now 30, he will be on his way down from here on in and there is no point in renewing his contract, the fact is that, whilst all of that might be true, they don’t really have anybody to replace him with at the moment. The only other player, who has played at right back so far this season has been Carl Jenkinson and he is unlikely to ease any fears that the Arsenal fans might have about the Frenchman leaving.
If Arsenal were to not renew his contract, which isn’t looking likely at the moment, that might mean that they will have to splash the cash in January or at the very least in the Summer on a new player, who will have to get accustomed to their style of play and the continuity and defensive shape that have had so far this season will be lost.