Birmingham left it late to knock Derby out of the FA Cup fifth round, while Reading were held by West Brom.
Birmingham came from a goal down to defeat Derby 2-1 at Pride Park.
Blues defender Scott Dann equalised after 73 minutes and just when the Championship side were contemplating a replay at St Andrews, Liam Ridgewell scored an injury time winner for the visitors.
Reading took the lead against high-flying Championship rivals West Brom at the Madejski Stadium after only ten seconds, but eventually had to settle for a 2-2 draw.
The Royals Jimmy Kebe scored early on, but Robert Koren equalised on 18 minutes.
Reading were then reduced to 10 men shortly after half-time when forward Shane Long was sent off.
But numerical parity was restored when West Brom substitute Youssouf Mulumbu received a second yellow card in the 61st minute.
Reading took advantage and scored with 17 minutes remaining.
The Baggies, though, hit back with three minutes left when Joe Mattock grabbed a dramatic equaliser.