The 59-year-old Scotsman, while taking care not to reveal which of the shot-stoppers he will play in tonight's friendly against Belgium, said that he had reached an "amicable" agreement with the two men to give them one game each.
This means that whichever plays tonight, the other will play in Scotland's opening UEFA Nations League fixture against Albania on Monday.
"It is a tough decision, but I'm in cahoots with Stevie Woods the goalie coach," said McLeish. "He is very fair with the two experienced goalies and Jordan Archer, as well.
"Stevie and I had big discussions a couple of weeks ago before the squad assembled about how we play this.
"It's difficult when you've got two goalies of a tremendous level. England had that problem way back in the day with (Peter) Shilton and (Ray) Clemence and it was one [game] each.
"There were eras where it worked out for the coach. I don't want to lose any of our keepers and have the ideal solution. I want these two guys to be around for as long as possible.
"For these two games we have had an amicable agreement.
"We will wait to see how the games go and see what suits the style of play we have in a game. If somebody has 40 world-class saves against Belgium then he might have nailed his position. It's a very difficult decision.
"It's so difficult for me to say that, ongoing, I can definitely pick one above the other."
While Celtic number one Gordon was McLeish's choice for the revent World Cup qualification campaign, McGregor did his best to give the manager a tough decision with an outstanding performance for Rangers in their Old Firm derby defeat on Sunday.