Barnsley boss Keith Hill endured a Christmas to forget after a devastating defeat saw his side slip further towards the foot of the tree.
A double from Birmingham defender Curtis Davies and another dose of dreadful defending saw Reds slip to 23rd place in the Championship.
The frustration was palpable among the Oakwell faithful. Instead of opening up a much-needed Christmas gift, they found only a lump of coal –their team dominating proceedings yet failing to gain any kind of reward.
Barnsley have only themselves to blame. A failure to fulfil even the basic defensive requirements from set pieces twice allowed the otherwise toothless visitors to capitalise.
And the festive misery was only compounded by a missed penalty from top scorer Craig Davies, meaning Reds were unable to add to Jonathan Greening’s first-half strike.
Although Hill will have wanted to keep changes to a minimum following the previous week’s win at Millwall, he was forced into a couple of key switches.
Injury to Martin Cranie and Stephen Foster’s suspension necessitated the introduction of Jimmy McNulty in the heart of the defence and Greening in midfield.
Despite that, Barnsley started brightly, taking every opportunity to test a Birmingham side which hadn’t won away since a 1-0 triumph at Leeds in October.
While the visitors relied heavily on the obvious threat posed by towering striker Nikola Zigic, Reds had more joy utilising the subtle smarts of Marcus Tudgay.
The goal-hungry poacher troubled the defence with his sharp movement and was eagerly fed by his hardworking teammates.
As a result, Tudgay twice went close to breaking the deadlock early on.
Drifting into space to meet a Scott Golbourne cross, his header was blocked by a defender and Stephen Dawson’s volleyed follow-up was held by Birmingham keeper Jack Butland.
If that particular effort proved comfortable for Butland, a second Tudgay header brought the best out of the talented young England international.
This time the Barnsley striker found the target after getting his head to a Dawson cross and Butland got down sharply to turn the ball away.
Despite their dominance, Reds simply could not take advantage.
Jim O’Brien dragged a disappointing shot wide from 25 yards, while David Perkins came within a whisker of getting a telling touch when Tudgay knocked down a Bobby Hassell free kick.
Due to their continued struggles in open play, Birmingham’s only threat came from corners and it was one such set piece which delivered a cruel blow to Barnsley.
Robert Hall delivered an accurate ball into the box and Curtis Davies rose unmarked to place a glancing header past Luke Steele for an undeserved lead on 35 minutes.
The response, however, was almost immediate.
A potent attacking move saw Golbourne get to the by-line and cut the ball back to Dawson.
His shot was blocked, sparking a mad scramble in the penalty box but Greening kept a cool head when the ball broke to drive home his first Reds goal.
Unfortunately, Greening wasn’t quite so accurate when another opportunity fell his way, pulling a shot wide of the post following O’Brien’s threatening cross.
Reds went in at the break without the reward their efforts so richly deserved but almost rectified the situation moments after the break.
Tudgay chipped a clever ball across the box but Chris Dagnall couldn’t direct his shot on target after sliding in to meet the fast-moving ball.
Hassell also failed with an extremely ambitious effort, attempting a lob from 45 yards after Birmingham had given the ball away while trying to release substitute Chris Burke on the counter.
Curtis Davies also produced a superb block to keep out a shot from John Stones before Hill decided to change things up, introducing top scorer Craig Davies and Matty Done for Dagnall and David Perkins.
And Davies should have made his presence felt after winning a penalty when his header was handled inside the box by Steven Caldwell.
But his spot-kick was all power and no placement, sent high over the top of the goal as the Oakwell faithful began to experience that familiar sinking feeling.
Punishment was swift in coming as another free kick produced yet another defensive failure.
Once more, Hall and Curtis Davies combined to devastating effect as the defender found enough space to score with another free header.
Barnsley’s best efforts failed to salvage a point, Davies sending a late free kick into the Birmingham wall just before the final whistle sounded.
Barnsley [4-4-2]: Steele 6; Stones 6, Hassell 6, McNulty 6, Golbourne 7; Perkins 8 (Done 68, 6), Dawson 7, Greening 6, O’Brien 6; Dagnall 6 (Davies 68, 5), Tudgay 7.
Birmingham [4-4-2]: Butland 8; Robinson 6, Caldwell 7, Davies 8, Hancox 6; Hall 7 (Gomis 85), Elliott 6, Mullins 6, Reilly 6, Redmond 6 (Burke 53, 6), Zigic 6.