Their latest home setback continued the trend from 2020, when they won just three times at home in the Championship, out of 22 games, taking just 16 points out of 66.

Karanka rang the changes after Tuesday's 4-0 home thrashing to Derby, with just four survivors starting this game.

But despite the change in personnel, there was a familiar start from Blues.

Blackburn, who went into the game as the Championship's joint-highest scorers with 36 goals, increased their tally in the 10th minute.

In a swift counter-attack, Harvey Elliott slotted Armstrong through on the left and the striker advanced before drawing goalkeeper Neil Etheridge and coolly slotted across him into the far bottom corner.

In truth, Birmingham were still reeling from a penalty appeal that fell on deaf ears after a challenge from ex-Blues player Amari'i Bell on Ivan Sanchez.

There was certainly contact but the referee's assistant was well placed and did not flag.

Armstrong's goal meant he has matched his total from the whole of 2019-20, but from just 22 games.

Rovers continued to pose a far greater threat and Sam Gallagher produced an outrageous effort when he flicked the ball over a defender and juggled it before sending a volley on top of the net from 25 yards.

The lively Armstrong was denied a second when he nutmegged a defender deep inside the penalty area only to see his toe-poked effort blocked by Etheridge.

Birmingham's first threat came in the 37th minute when Ivan Sunjic's skidding drive was tipped away by goalkeeper Thomas Kaminski.

They followed that up with a free-kick from Sanchez that curled just wide and above the angle.

Birmingham started the second half in improved form and Jonathan Leko saw a curling, rising effort deflected fractionally wide.

But they were not able to sustain it and their awful home form was summed up when defender Jake Clarke-Salter looped a free header comfortably over the bar from Sanchez's corner.

Substitute Scott Hogan was denied an 88th-minute equaliser when Kaminski saved at his feet as the striker went to take the ball around him in a one-on-one.

Dack punished them when he curled home a sweet shot from the edge of the box in the second minute of time added on after fellow substitute Tyrhys Dolan broke and ran at the defence.