Carr needed daily injections to ensure he was fit enough to play in City's opening five Premier League games.
He was rested for the midweek Carling Cup win over MK Dons but will return for Saturday's home league clash with Wigan.
McLeish said: "Stephen has been taking injections for the past month every day. It is ridiculous the pain he is enduring.
"To endure the injections alone is quite a feat because these cortisones go right in deep and it is quite a tender area on his little toe.
"Stevie has still been playing to a high standard in training and in games.
"Unfortunately a wee bit of indecision cost us a goal at the weekend against West Brom. But it is very rare you see him make a mistake."
McLeish is hoping the forthcoming two-week international break will allow Carr's injury to heal.
He said: "It is difficult to get respite. We have tried to rest him in between games.
"But he is the type of boy who doesn't want to miss training so you are in a bit of a Catch-22 situation.
"Hopefully the international break will give him a chance to heal properly."
McLeish is encouraged to have striker Kevin Phillips back at his disposal after recovering from a torn thigh muscle.
He made his comeback in the final 20 minutes against MK Dons and looked sharp.
McLeish said: "It doesn't matter if Kevin gets on for only a couple of minutes. He will always try to get a shot away.
"You saw the man's hunger for goals, you've seen it all of his career, and he got into some bright positions against MK Dons."
Phillips signed a new one-year contract in the summer after showing his worth as an impact player from the bench last season.