McCall took over from caretaker boss Kenny McDowall last week and despite starting brightly on Saturday managed only a 1-1 draw against Livingston.
The Ibrox outfit go in search of only their second win in nine games against Alloa and McCall says places are up for grabs.
“We will change personnel over the next few weeks,” said McCall, who welcomes back keeper Cammy Bell but has seen Haris Vuckic and Sebastien Faure ruled out with injuries.
“I need to see what the guys look like so most of the squad will get a game. That’s not about giving someone a game just for the sake of it.
“There might be a couple of players who will feel they merit a chance when they’ve not had one, so how can I judge them if I don’t see them?
“Until we get the right formula and see players deserving a jersey, I will make changes.
“We’ve got a couple of injuries for tomorrow night so that will be the case already.
“We’re evaluating all the time in training and games but we have to do it quickly. We have to get back up to a position where we can win football matches.”