And, with the club captain seemingly keen to pack his bags, Arsenal might now need to completely rethink their transfer plans.
The Gunners confirmed earlier today that the France international won’t fly to the USA with his team-mates.
An official statement said: “Laurent Koscielny has refused to travel to the US for our pre-season tour.
“We are very disappointed by Laurent’s actions, which are against our clear instructions.
“Arsenal ace Laurent Koscielny could leave the club”
“We hope to resolve this matter and will not be providing any further comment at this time.”
Koscielny, 33, has now entered the final year of his contract but fancies a move away from north London.
Unai Emery appeared to have lined up the ideal long-term replacement for the France international.
William Saliba, who is regarded as one of the hottest defensive prospects in Europe, is bound for the Emirates.
But given his relative inexperience, 18-year-old Saliba was set to return to Saint-Etienne on loan.
Saliba is viewed as a natural heir to Koscielny, but made only 18 appearances in Ligue 1 last season.
Ideally, Koscielny would have left the club next summer.
Saliba could have then slotted in after another season of competitive first-team football in France.
Koscielny’s actions might have thrown a major spanner in the works, though.
Arsenal will now need to decide whether to stick with their initial plan and loan Saliba back out if Koscielny is sold.
Alternatively, if Koscielny departs, Emery could be tempted to throw Saliba into the Gunners first team.
Emery has been told to be thrifty in the transfer market this summer.
The Spaniard will be well aware that signing a centre-back of Koscielny’s experience won’t be cheap.
Arsenal are also still hoping to snare a new full-back as Emery frantically attempts to juggle the finances.
Kieran Tierney, 22, remains a top target but a deal is yet to be sealed.
Emery is also closing in on Real Madrid midfielder Dani Ceballos.
A cost-saving loan deal for the 22-year-old Spaniard looks on the cards, but rivals Tottenham are also sniffing around.
Ultimately, Koscielny’s sabre rattling isn’t a disaster for Emery.
But make no mistake, it’s an unwelcome headache in what is already a complicated transfer window for the ex-Sevilla man.