McCoist should discover the full extent of the ankle injury suffered by new signing David Templeton early this week.
The winger pulled up in the opening 10 minutes of his team's Third Division game with Annan at Galabank on Saturday.
If the 23-year-old is ruled out in the long-term, it will be a big blow to McCoist at the start of a hectic schedule of matches.
He is already without Andy Little after the forward, who has scored eight goals in as many games for his boyhood heroes, picked up an ankle injury on international duty with Northern Ireland.
Elsewhere, Greek right back Anestis Argyriou is out of action after sustaining a hamstring injury during training.
McCoist could be left with a decidedly threadbare-looking squad ahead of what is a demanding and crucial spell of matches for Rangers.
They take on First Division Queen of the South in the Ramsdens Cup quarter-final at Ibrox tomorrow evening.
On Sunday they return to league duty with a game against Montrose at home that will be screened live by ESPN.
On Wednesday week they play Clydesdale Bank Premier League leaders Motherwell in the Scottish Communities League Cup.
Three days after that Rangers open their account in the William Hill Scottish Cup with a match at Highland League rivals Forres Mechanics.
McCoist was disappointed at the number of players he was able to bring in before the transfer window closed on August 31.
He had hoped to swell his squad before a 12 month transfer ban, imposed by the SFA for the sins of the ill-fated Craig Whyte era, kicked in. The gaffer only manager to bring in two new players – Templeton and Francesco Stella.
He lost captain Carlos Bocanegra to Racing Santander on loan. At the time, McCoist expressed concerns about his team's ability to deal with any injuries they may suffer or bans they may incur.
Rangers will only be allowed to sign free agents come next September at the end of the transfer ban and will be unable to buy a player until January, 2014.
Rangers fans had been looking forward to the League Cup and the Scottish Cup in the campaign.
However, if their injury situation fails to improve, it is unlikely they will be able to progress far in those tournaments.