Birmingham knocked city rivals Aston Villa out of the League Cup with a 2-1 victory at St Andrews on Wedneday. The result threatened to be overshadowed by a pitch invasion after the final whistle that saw thousands of fans spill out onto the pitch.
Nikola Zagic's goal six minutes from time saw Birmingham through to the last four and gave the Blues a measure of revenge over Villa manager Gerard Houllier.
Serbia international Zigic's deflected shot settled the tie after Villa's Gabriel Agbonlahor had cancelled out an early Sebastian Larsson penalty. Houllier was Liverpool's manager when they defeated Birmingham in the 2001 League Cup final.
In Wednesday's other quarter-final, under-fire manager Roy Keane guided second-tier Ipswich to a 1-0 win over Premier League side West Brom at Portman Road thanks to Grant Leadbitter's second-half penalty.
Birmingham will now play West Ham, 4-0 conquerors of holders Manchester United on Tuesday, in a two-legged semi-final next month when Ipswich will face Arsenal after the Gunners 2-0 win over Wigan.
The Blues' win over Villa was their first over their local rivals for five and a half years. They went ahead against the run of play after Lee Bowyer was brought down by Villa captain Richard Dunne. Larsson sent the resulting penalty low to beat American keeper Brad Friedel.
Birmingham thought they'd scored again after 28 minutes when Zigic's low shot was pulled back by Friedel when replays suggested it may have crossed the goal-line. But a linesman's raised flag led to Liam Ridgewell being ruled offside.
Villa then cashed in when, after the half-hour mark, Agbonlahor latched onto Jonathan Hogg's through-ball and struck a powerful shot past Ben Foster. Both sides had further chances to score before Cameron Jerome sprinted down the right and his low cross found Zigic, whose shot deflected off Luke Young and looped over Friedel.
Villa nearly pushed the tie into extra-time when Ciaran Clark headed just over from Stewart Downing's cross.