Arsenal are looking to bolster their defences this summer after Unai Emery made demands.
The Spaniard is keen to sign a new centre-back and a left-back – but Koscielny has thrown those plans into disarray.
The 33-year-old stunned Emirates chiefs when he told the club he would not be joining them on their pre-season tour of the United States.
Koscielny refused to board the plane with his team-mates in a wild turn of events, with the Frenchman desperate to leave the club.
And the Gunners are facing up to the prospect of losing their club captain after he agreed terms with Rennes, according to RMC Sport.
Koscielny has one year left on his contract as he strives to release himself from his final season.
But Arsenal have decided they will not accept anything less than £9m for him, which could prove tricky for Rennes.
The Ligue 1 outfit are not blessed with funds and will be hoping the Gunners and Koscielny can come to an amicable understanding.
But the manner in which the France international has gone about his business suggests that it could be anything but.
It has left the Arsenal fanbase up in arms as club legend Arsene Wenger even admitted his shock.
“I am very surprised by the current situation,” Wenger told L’Equipe.
“I do not know the whole story, but Laurent’s behaviour with me has always been beyond reproach. I think highly of Laurent as a man.”
In the meantime, Emery has to make a decision over who will be the new club captain.
Granit Xhaka has emerged as the leading choice while Rob Holding has also made a pledge.
Emery has stated that he wants five players capable of wearing the armband, and wants one Englishman to don it as well.
“I want one English player in these five captains,” he said. “Last year [Granit] Xhaka, Mesut [Ozil] and Nacho [Monreal] were working as captains.
“But after Aaron Ramsey and Petr Cech left – and possibly Laurent Koscielny – I will want more.
“An English player who grew up in our academy can understand the English spirit and Arsenal values. These are the qualities and more [we want].”