The Ibrox side are to carry out an investigation and the Light Blues boss was unable to go into any details on the situation.
Reports have suggested the investigation relates to last summer's transfer activity.
McCoist said: "Neil has been suspended by the club pending an investigation.
"It's a really sensitive matter and that's all I can say on it."
Recent weeks have also seen the departures of youth coach Tommy Wilson and physiotherapist Pip Yeates.
Asked about concerns over changes to his backroom staff, McCoist said: "We have to be in position ready to go for the start of next season, that's my concern.
"Staff at football clubs, and in any work force, come and go. I fully appreciate that.
"That said, in terms of the recruitment of our players, the next two or three years will be the most important time in the club's history.
"So we have to be ready for that and we will be."
- Sports & Recreation