McLeish's League Cup winners, who stunned Arsenal a fortnight ago, will book their second trip to Wembley if they overcome Owen Coyle's team at St Andrew's.
The Blues manager could be forced to select from a severely depleted squad, however, with first-team regulars Barry Ferguson, Craig Gardner, Stephen Carr, Liam Ridgewell, Lee Bowyer, Keith Fahey, Nikola Zigic and David Bentley all doubtful and Scott Dann, James McFadden and Alex Hleb definitely out.
But, despite his 17th-placed team being entrenched in a Premier League relegation fight, McLeish insists he will resist the temptation to rest any of his stars for their battle to beat the drop.
He said: "It is the worst injury situation in my time at the club. It is something you can't control, injuries as a manager. In terms of suspensions, you can work on discipline; you can try to make sure you cut out too many yellow and red cards."
"But the injuries are things that are difficult to legislate for. The league is more important to us. There is no doubt about it."
"But I owe it to the Birmingham fans to play the strongest team available. It might not be strong enough to win. I could play my best team against Bolton, and we could still lose because they are a good side. We could lose but we don't plan to. We are going to try to win this game."
Bentley, on loan from Tottenham, is "touch and go" after limping off with a groin problem early on in Wednesday's 1-1 draw at Everton.
And McLeish hopes midfield maestro Ferguson will get the green light after missing their last two games with a broken rib.
"Barry is good, he trained on Thursday and looked very mobile. He took the injection, so he has got a bit of the freeze in his side which is saving him from the pain. As regards Saturday, he will decide last minute," he said.
Coyle says Birmingham's Wembley triumph proves that the monopoly enjoyed by the top-four can be halted.
The Bolton manager is motivated by the prospect of unfashionable clubs, such as Bolton, now standing a realistic chance of lifting domestic silverware.
"Everybody would have looked at that and felt good about it. There is always a tendency, rightly so, that even when a club gets to a final, the perception is that the elite club will still win on the day," Coyle said.
"And it wasn't only that Birmingham won. It was the way they went about it. I think that is a great boost for anybody. It serves notice that it's not just the elite four or five clubs who can win the trophies, and that has to be the motivation for anybody."
It was opposite number McLeish who helped Coyle land his first job in English football, recommending Burnley to take a punt on his countryman back in 2007.
Despite playing a key part in his development that eventually saw him move to the Reebok Stadium, Coyle insists his close friendship with his fellow Scot will be on the backburner.
"I have such a high regard for him but he knows for the duration of this match I'll be doing everything I can to progress to the semi-finals," he added.
"We are one step away from Wembley and for the club it's an opportunity for a strong, positive finish to the season."
Birmingham cup double hopes hit by injuries
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