Calum Chambers out for nine months means Arsenal have to test the transfer market.
The news that Calum Chambers will be out for nine months is a body blow but there is a silver lining, well, for the fans anyway.
Obviously, it is harsh on Chambers and no one wants him to be injured but now that he is it is untenable that the club do not at least make an effort to sign a replacement.
Signing David Luiz last summer was a mistake and certainly not enough and allowing Wiliam Saliba to stay in France on loan hardly helped either.
The signing of Kieran Tierney was positive but he is also injured and therefore the Arsenal defence is severely under strength and remains a huge weak point in the team.
Shkodran Mustafi remains an option, Rob Holding should be back soon and there is Konstantinos Mavropanos which means there are at least five centre backs but even Mikel Arteta will know that a five of Luiz, Sokratis, Mustafi, Holding and Mavropanos is not going to cut it.
Arsenal desperately needs a seasoned centre half that knows his way around the Premier League, no point buying in January someone that needs time to adapt.
There is no guarantee that Arsenal will be able to sign a quality centre half this winter but they have to at least try.
The defence cannot be left in the condition it currently is without new additions, it simply is not good enough.
Do not fall into the trap of thinking that after last night that all of a sudden the Arsenal defenders are world-class, they are not, they are poor and a major overhaul is required.
So, it is a downer that Chambers is injured long term but at least the club will now have to confront the challenge of fixing the glaring deficiencies in the Arsenal defence.