But others may have to follow them out of the exit door before McCoist can add to the seven players he has recruited so far.
Mather told RangersTV: "More of the squad could be moving on. There's potential for that, I'm not going to sit here and hide it.
"Ally has made no secret of the fact he'd like to make one or two more signings if possible and in principle I have no problem with that. We do have to balance the books though and look at it accordingly. It would be good for the stability of the club if we can get a couple more moved on as well."
A transfer embargo means Rangers are unable to register their new signings - who must be free agents - until September 1.
Until then, two trialists can be fielded in one game, albeit with restrictions on how many matches each individual can feature in.
Mather added: "It is going to be a juggling act and we only found out recently that the trialists will be able to play after all. Under SPL rules they couldn't but under SFL rules they could. We're only going to be able to play two of the new players as trialists in each game so we'll need to balance things there.
"What we have to do is make decisions based upon the longevity of the club rather than just a four-week period. We will play the cards as they come at us rather than worry about the first month only at the moment. It's a long season."