Unai Emery wants to complete two signings before Thursday’s transfer deadline.
The Gunners have just agreed a fee to allow Laurent Koscielny to join Bordeaux for £4.6m.
The 33 year-old’s departure became inevitable once he refused to join his teammates for Arsenal’s pre-season tour of the USA.
He departs the club having made 353 appearances and scored 27 goals since joining from Lorient in the summer of 2010 for a fee of around £10m.
Emery was already in the market for a centre-half and it is now critical the Spaniard recruits a central-defender before the window slams shut.
Reports say the Gunners have retained interest in Celtic left-back Kieran Tierney, for whom they have had two bids rejected, and also want a centre-back.
Arsenal had a £15m offer rebuffed for the 22 year-old with a follow-up approach of £25m also turned down because the offer was heavily reliant on add-ons.
Meanwhile, the north Londoners have also made enquiries about Juventus centre-half Daniele Rugani and RB Leipzig’s Dayot Upamecano as they seek to strengthen in central defence.
The first game of the new season kicks off with a trip to Newcastle on Sunday (14:00 KO).