Birmingham kept up the pressure on leaders Wolves and moved seven points clear of Reading by beating Doncaster.
Blues' Maik Taylor saved well from Martin Woods before Cameron Jerome powerfully headed in from 12 yards.
Hameur Bouazza doubled the lead, rolling in after he intercepted Gareth Roberts' shocking back-pass.
Matt Mills had a header cleared off the line and Taylor saved from Mark Wilson and James Hayter as Birmingham comfortably held on for the points.
Doncaster manager Sean O'Driscoll
"You have to give them credit because they've watched us numerous times. They flooded the midfield to combat us which I suppose is a bit of a compliment and they were successful with the tactics they adopted.
"We were a bit naive in the way we tried to play against them but they are an extremely professional side and we are learning all the time."
"They deserved their win and it's frustrating for us when things go wrong but there is no point screaming and shouting at players - we just have to learn to improve."
Birmingham manager Alex McLeish:
"We may not be the prettiest side in the world to watch but we have perseverance, resilience and a never-say-die attitude.
"It was important tactically we played the way we did this because Doncaster are a formidable side.
"We coped with them very well - we've given ourselves every chance."
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