The Senegal international midfielder, playing in just his second game for Blues since arriving from Anfield during the January transfer window, was booked by referee Steve Dunn for a late challenge on Baggies winger Kieron Richardson 26 minutes into the game at The Hawthorns on sunday lunchtime.
Diao had already got three cautions against his name this season when arriving at Blues and adding those to sundays yellow card brings his seasons tally to four - just one short of an automatic one game ban.
YELLOW CARDS:
Matthew Upson - 6
Damien Johnson - 6
Emile Heskey - 5
David Dunn - 4
Salif Diao - 4
Muzzy Izzet - 3
Darren Carter - 3
Olivier Tebily - 2
Darren Anderton -2
Jermaine Pennant - 2
Clinton Morrison - 1
Martin Taylor - 1
Stan Lazaridis - 1
Mario Melchiot - 1
Stephen Clemence - 1
Medhi Nafti -1
Walter Pandiani -1
RED CARDS:
Damien Johnson - 1 (Charlton, home)
Muzzy Izzet - 1 (Everton, home)