Rotherham still on top here as Angus Gunn rushes off his line to good effect to thwart Conor Washington.
Cardiff's Jaden Philogene is wrestled down in the box by Sunderland defender Danny Batth, who is shown a yellow.
Former Stoke City loanee Scott Hogan scores against them for Birmingham.
A defensive error lets him in but Hogan is alert and it's a ruthless finish to put the visitors ahead.
The last time Matt Grimes did not feature in a Championship game for Swansea was way back in October 2020, 104 second-tier outings ago.