Blues endured a torrid afternoon at Elland Road going down 4-0 to Leeds United in the Sky Bet Championship.
First-half strikes from Ross McCormack, Rodolph Austin and Matt Smith all but secured the points before Smith doubled his tally in the second period.
Lee Clark made five changes from the side that started the 2-1 home defeat to Bolton Wanderers before the International break, along with a switch in formation.
The manager opted to revert to a back three in which Kyle Bartley lined-up alongside Dan Burn and Paul Robinson. The rest of the changes saw Paul Caddis, Wade Elliott, Lee Novak and Olly Lee, making his first league start for Blues, return to action.
The first chance of the afternoon fell to the home side and should have resulted in the opening goal. Dan Burn's mis-cued clearance allowed Ross McCormack to run clean through on goal but Darren Randolph kept out the striker's effort.
It was a sign of things to come as Leeds began to assert themselves and continue to threaten the Blues goal. First Jason Pearce cleared the crossbar with a stooping header from 6 yards before McCormack was once again thwarted by Randolph.
Blues' first sight of goal came through Chris Burke, the winger was played through by Jesse Lingard but dragged his effort wide of the post.
After 18 minutes the hosts opened the scoring. Randolph came out to deal with a ball over the top for Matt Smith but his touch fell to Rodolph Austin, and the Leeds skipper teed up McCormack to slot the ball into an empty net from 25 yards.
Leeds doubled their advantage just after the half-hour mark and this time it was roles reversed. McCormack turned provider as his cross found the unmarked Austin who headed past the despairing Randolph.
On the stroke of half-time Blues' task was made all but impossible. Randolph repelled McCormack's initial effort but was powerless to stop Matt Smith firing home the rebound and giving his side a three-goal advantage heading into the break.
Lee Clark made two changes at half-time. Dan Burn and Lee Novak were replaced by Andy Shinnie and Nikola Zigic and the two immediately combined to almost pull a goal back. Shinnie collected Zigic's flick-on and curled a shot just wide of Paddy Kenny's post.
Blues continued to look for a way back into the game and came close through Wade Elliott's shot from 20 yards which whistled over the crossbar.
The home side were dangerous on the break though and Randolph, not for the first time, had to be at his best to keep out Austin.
Clark must have though his side were back in the game when Burke's chipped effort had Paddy Kenny beaten all ends up but Tom Lees got back brilliantly to head the ball off the line.
David Murphy was next to go close. The defender struck the post with a free-kick from 30 yards.
Blues saw a flurry of golden chances come and go but they couldn't convert them into goals to give the travelling fans any hope of a comeback.
If there were any hopes of a dramatic turnaround they were dashed with 15 minutes remaining. Alex Mowatt picked out Matt Smith at the back post and the striker thundered his header into the back of the net.
Lee Clark's side paid the price for a poor first-half performance and head back to Birmingham empty handed.