Ziyech was in Paris on deadline day to complete a loan move to PSG but the deal collapsed after Chelsea failed to file the necessary documents in time.
The Parisians have accused Chelsea of negligence and claimed that the Blues twice sent them incomplete or wrong documents before sending the right set of files but by that time the window had closed.
The Moroccan could now spend the rest of the season at Chelsea and McCoist stressed that he needs to accept his current reality as soon as possible.
He insisted that Ziyech cannot do anything about it now and if he moans about it for too long, the Chelsea fans will soon turn against him.
McCoist said on talkSPORT: “The only thing you can do is get his head around it, accept and work your socks off and maybe it will happen in the summer.
“That’s all he can do.
“There is no use sitting moping and moaning because he will not be helping himself and the fans will completely turn against him.
“There needs to be an acceptance that a mistake has been made but there is nothing he can do about it now.”
Ziyech will hope to convince Chelsea boss Graham Potter to give him more opportunities despite the club signing a plethora of new players in the winter window.
