Chris Hughton has this season become accustomed to beating the odds.
After being appointed in June, Hughton has seen 28 players leave either permanently or on loan, following last season's relegation.
The Blues took a dramatic turn following their League Cup win over Arsenal in February, losing seven of their last 12 games to consign them to relegation.
With a host of players leaving a squad who struggled to such an extent last season, bookmakers made the club 22/1 to return to the Premier League at the first time of asking.
Against the backdrop of a club president being charged with money laundering and his assets subsequently being frozen, the club failing to file last season's accounts and being slapped with a transfer embargo, it's barely believable the club is still functioning, let alone sustaining a promotion push from the Championship.
Hence when faced with Chelsea at St Andrew's on Tuesday night, Hughton needn't be phased by the proposition of taking on a side who topped the Premier League tree less than two years ago.
While Birmingham came into the season hoping they'd just come out of the other side, Andre Villas-Boas will have been hoping for exactly the same thing.
Having now rid of the Portuguese boss, Chelsea are scrambling towards the summer, while having to pick up the pieces on the way.
Tonight they face the prospect of being overcome by a team who by comparison have larger problems, and therefore have substantially less to lose.
It's a carefree attitude that's allowed Birmingham to stray away from the days of Alec McLeish with the enterprising Nathan Redmond and Jordon Mutch spearheading their assault on the top six.
The context of the FA Cup gives Birmingham even more license to compile Chelsea's misery, but an upset be the smallest jewell in Hughton's crown after a season of defying the odds.