Blues deservedly led the Baggies 1-0 at half time through a Cameron Jerome goal but some sloppy second half play resulted in the hosts running out comfortable 3-1 winners - the first defeat of the season coming just hours after the Blues boss had signed a new three year contract with the club.
"I'm delighted to put pen to paper," the City manager told Sky Sports after the game.
"The players have worked wonders in the last year but they know performances like in the second half will see us in a dogfight.
"But what they have in their locker is they can bounce back from setbacks time and time again.
"When you lose goals like the first two, you can't legislate (for that). It doesn't matter what change was made.
"In the end West Brom looked comfortable and were the better side because we lost our shape and were open at the end.
"We huffed and puffed but we didn't look like we could cause them any problems and that's the disappointing thing."