Mikel Arteta has been told he needs to sign a new centre back to Arsenal this week by Martin Keown.
The Gunners have been left short at the back with Calum Chambers out for the rest of the season with a knee injury and Shkodran Mustafi taken off on a stretcher against Bournemouth on Monday.
Mustafi collided with keeper Emiliano Martinez and appeared to damage his ankle - with a scan likely to show up the extent of the problem over the next couple of days.
Arteta said: "I hope I'm wrong but when a central defender is taken off on a stretcher it is not usually good.
"We will find out more in the next days and we will assess it."
Fellow defenders Kieran Tierney and Sead Kolasinac are also sidelined.
Therefore, Arteta is likely to attempt a late deal for a centre back before the January transfer window slams shut on Friday.
Spanish ace Pablo Mari is the most probable target to come in, although the ongoing negotiations between the Gunners and Flamengo are in danger of collpasing.
Arsenal had previously agreed a £7.5million fee with Flamengo, with Mari travelling to London, only for the Gunners to renege on the deal.
Gunners legend Keown has pleaded with his former club to splash the cash to give them hope of saving their season.
Keown told BT Sport: "Numerically, Arsenal now need to go and sign a central defender if they didn’t need one already.
"That will determine it. You need to have bodies now. There’s massive goals ahead for the rest of the season.
"You’ve got the Europa League where if you win that you get back in the Champions League, you can fight for the top-four – maybe that’s gone – but you’ve got to get back into Europe and the FA Cup itself.
"There is still so much to fight for."
