And a clause in his contract, inserted by the Gunners, suggests the French midfielder will not be returning to north London.
The 22-year-old's goodbye message took social media by surprise on Monday when wrote directly to the Arsenal fans.
"Thank you Arsenal. Thanks for everything!" he said.
"I discovered and learned so much during my time here. It would be impossible to list everything without forgetting one memory or word… but I will never forget any minute spent with the Gunners jersey.
"I will never forget the Emirates Stadium. I will never forget the fans. I won't forget the city."
Confirmation of the deal is expected today.
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!