The Gunners have seemingly beaten Premier League rivals Wolves to the signing of 25-year-old Rugani.
Frenchman Koscielny, who refused to travel for the club's pre-season tour, has completed a £4.6million move to Bordeaux.
Arsenal have been on the hunt for a replacement ahead of the transfer window closing on Thursday evening.
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!