Keith Fahey's goal just before half-time handed promotion-chasing Birmingham victory against struggling Southampton at St Andrew's.
Fahey scored what proved to be the winner when he drilled in Cameron Jerome's clever ball from the left.
Blues also went close when striker Scott Sinclair hit the post in the closing stages.
Southampton rarely tested the Birmingham goal, although Jason Euell had his lob cleared off the line.
Birmingham City manager Alex McLeish: "The last four days have been excellent. The players have responded to the challenge.
"We have wasted some good opportunities but we are still in a strong challenging position and I am proud of them. The back five were rock solid.
"No-one should forget we have lost key players for long parts of the season and we have been hard done by."
Southampton manager Mark Wotte: "What concerned me was conceding a goal just before half-time.
"We cannot concede a goal like that after they had played for 10 minutes with only 10 men when Lee Carsley was off the field.
"Birmingham are a strong side but we were not strong enough up front to score a goal. Now I have to lift the side for the two home games against QPR and Derby."
Birmingham: Maik Taylor, Carr, Jaidi, Martin Taylor, Queudrue, Larsson, Carsley, Bowyer, Fahey (Sinclair 68), Jerome (Bouazza 76), Bent (Costly 18). Subs Not Used: Doyle, De la Cruz.
Venue: St Andrew's Date: Saturday, 7 March Kick-off: 1500 GMT Coverage: Live commentary on BBC Solent 96.1 FM & Hants DAB; Score updates on BBC Radio 5 Live & BBC Sport website
Birmingham team news to follow later.
Southampton have a minor injury worry over defender Jan-Paul Saeijs, but they are hopeful the Dutchman will be fit for the trip to St Andrew's.
Midfielder Adam Lallana missed the midweek win at Ipswich and is once again struggling to be fit.
Southampton head coach Mark Wotte: "I love to play the best teams in the league, the challenge is so big and there is so much to win, so we're looking forward to this game.
"They are a big club, they have a big stadium and lots of fans, but they are under even more pressure than us I think, they need to get back to the Premier League.
"We need to survive, but that's another kind of pressure. We're not afraid of playing them at all.
Two goals from Jason Euell and one from substitute Matthew Paterson secured an impressive victory for Southampton that severely dents Ipswich's promotion bid.
Euell headed home an Andrew Surman free-kick for his first before capitalising on a Pim Balkestein mistake to slot home his second.
Paterson drove in from the edge of the box to complete the rout.
Saints also had headers from Jan-Paul Saeijs and Chris Perry disallowed by referee Andy D'Urso for fouls.
Ipswich boss Jim Magilton told BBC Radio Suffolk: "It's certainly the worst since I became manager, without a shadow of a doubt. It was three (nil) going on six.
"It was not acceptable. The crowd had every right to voice their opinion.
"You have to have a few words after that performance. You want to know where it came from. It stunned the life out of me. I didn't see it coming."
Southampton boss Mark Wotte: "Jason Euell has done fantastically for us tonight. I am pleased with him.
"When I started this job I gave him a substitute role three times, and every time he had a good impact - so I put him in the first XI.
"His contract is expiring, so he has personal reasons to play well. He feels confident, like most of the players, and he has done brilliantly."
Ipswich: Richard Wright, Bruce, McAuley, Balkestein, David Wright, Norris, Miller, Quinn (Garvan 61), Civelli (Walters 46), Counago, Stead (Lisbie 46). Subs Not Used: Supple, Campo.
Jason Euall keeps Mark Kennedy at bay as the Saints take the spoils
A controversial penalty from David McGoldrick after 11 minutes earned struggling Southampton a vital win in their fight against relegation.
The result brought an end to Cardiff's 13-match unbeaten Championship run and hurt their play-off hopes.
Mark Kennedy was penalised for handling in his own goal area after good work from Jason Euell and McGoldrick struck.
The Saints climbed one place to third from bottom while Dave Jones' side dropped to sixth in the table.
Cardiff City boss Dave Jones: "I don't think we performed anywhere near what we are capable of. I think possibly four out-field players did their jobs and the rest didn't turn up today.
"It's hard to swallow... It's a harsh decision for the penalty when you're looking for a little bit of luck.
"I wished the linesman's eyes had been as sharp [in the second-half] as they were in the first-half because it's a clear-cut penalty when the [Southampton] lad hands it back to the keeper.
"... But full credit to Southampton - they worked harder than us and we didn't really cause the keeper any great concern."
Ivan Sproule's injury-time goal ensured Bristol City's unbeaten league run stretched to nine games while leaving Southampton deep in relegation trouble.
City's Bradley Orr saw an early penalty saved and Saints hit the post twice before Dele Adebola latched on to Gavin Williams' pass to put the Robins ahead.
Kayne McLaggon tested home keeper Adrian Basso after the break and Jason Euell missed a tap-in from six yards.
And Saints paid dearly when Sproule raced the length of the pitch to score.
Bristol City boss Gary Johnson:
"Southampton put us under pressure but we defended when we had to and earned our win.
"Things are going very well for us and we are confident about making the play-offs, not in an arrogant way, but because we have faith in one another."
Southampton manager Mark Wotte:
"I can't fault them for what they did in the second half. But we play to score goals and didn't, which is why we are in our current position.
"I think we have better quality strikers, but at the moment we are finding it hard to get goals and that has to change.
"I can't believe we lost. The least we should go home with is a point."
Venue: Vicarage Road Date: Saturday, 7 February Kick-off: 1500 GMT Coverage: Full-match commentary on BBC Radio Solent on 96.1fm & Hants DAB, & the odd score update on BBC Radio 5 Live & BBC Sport website
Saturday's Championship match between Watford and Southampton has been postponed following this week's adverse weather conditions.
According to a statement on the Watford website: "The risk to the general public if the game went ahead could have potentially been too high."
