Alfie May inspired Birmingham to a 6-2 win against 10-man Barnsley in Sky Bet League One at St Andrew’s.
Mael De Gevigney saw red in just the third minute after a last-man coming-together with Keshi Anderson.
Jay Stansfield fired Blues ahead from the penalty spot in the 32nd minute after Keshi Anderson was taken out by Kieren Flavell.
Davis Keillor-Dunn headed Barnsley level in the 35th minute after a near-post cross was headed back across the box.
A quickfire brace from May at the start of the second half had Blues 3-1 up by the 55th minute.
Just four minutes late, Barnsley pulled one back through Stephen Humphrys, whose effort at the near post snuck past Allsop.
Luke Harris converted with a powerful strike in the 72nd minute after driving down the right, before Kieran Dowell added a fifth in the 82nd minute.
Any lingering doubt was removed when Lukas Jutkiewicz added a sixth in the 89th minute after capitalising on a loose ball from his earlier effort.
