The 27-year-old, a £6million signing from Manchester United this summer, saved Morten Gamst Pedersen's penalty and pulled off a number of other impressive stops to ensure the Blues maintained an unbeaten home run that stretches back to last September.
McLeish is in a good position to judge the relative merits of the two men battling for the shirt for England's opening Euro 2012 qualifiers against Bulgaria and Switzerland next month having taken Hart on loan from Manchester City last season.
The Scot said: "Foster was excellent. The first home game and he's saved us points already. It's a brilliant start for him, he made the most brilliant penalty save.
"If it's him and Joe Hart that are vying for the England jersey at the next internationals, I think Joe's in pole position at the moment but with performances like that it's going to be a great battle between two great young goalkeepers."
Despite Foster's heroics, it was Rovers who took the lead in the 54th minute through Steven Nzonzi's header before Craig Gardner became Birmingham's second hero of the day with two goals in 14 minutes, leaving Rovers boss Sam Allardyce a frustrated man.
He said: "Ben Foster won them the game with his outstanding saves and our inability to convert chances into goals. We've completely dominated the game, created far more chances than Birmingham but failed to take them. And to boot we go and throw it all away.
"It's a typical Achilles heel of ours, not being able to take advantage of dominating the game and creating chances to win it, and today we've paid the price."
McLeish admitted the Blues had been somewhat fortunate to come away with three points but hailed the battling qualities of his side.
"They dominated our penalty box with their bombardment," he said.
"We tried to play it on the ground but even if we were the most silky team in the world today they would still have caused us problems because of the tactics they use, and they use them well.
"It was a tough game, we could have lost it. But again the players showed spirit and resilience - I need to find some new words because I used these words every week last season."
There was a debut today for man in the middle Michael Oliver, who at 25 became the youngest referee in Premier League history.
Oliver had little to do in a dire first half where the only real action of note was a Scott Dann header from Sebastian Larsson's corner that was well saved by Paul Robinson.
But the rookie referee became the centre of attention five minutes after the break when he spotted Nikola Zigic pulling Christopher Samba's shirt and awarded a penalty.
Pedersen struck it well but Foster did brilliantly to tip it onto the angle of post and bar.
Rovers were not to be denied. After Foster had saved an effort from Nzonzi, the same player got his head to the resulting corner to put the visitors ahead 54 minutes in.
It was a deserved lead but it lasted only three minutes as a long ball from Stephen Carr picked out James McFadden, who showed superb touch to volley the ball into the path of Gardner.
Nikola Kalinic hit the post with a free header from six yards for Rovers but it was Gardner who struck the winner with 19 minutes left as a speculative effort from 30 yards bounced in front of Robinson and into the far corner.
Allardyce was impressed by Oliver's display, saying: "I thought his performance was very encouraging. He gave fair decisions to each side and I don't think he got any major decisions wrong.
"It was obviously very brave to give the right decision for the penalty. In his first game in the Premier League he could have easily shirked away from that one but he was brave enough to see it and he was man enough to give it."