Bidding to bounce back from their Champions League elimination by Barcelona in mid-week, City were giving a huge helping hand when referee Neil Swarbrick sent off West Brom defender Gareth McAuley after only 89 seconds.
But it was Craig Dawson, West Brom’s number 25, who had committed a foul on Wilfried Bony (who then stumbled into number 23 McAuley), and Swarbrick confessed at half-time that he had sent off the wrong player.
“I was too far to see the red card incident. It is the referee’s decision,” City captain Vincent Kompany told BT Sport. “There was nothing to win today for us. We just had to do a good job and we didn’t fail.”
Bony made the breakthrough in the 27th minute, gathering a deflected pass from Fernando and hoisting a shot past West Brom goalkeeper Boaz Myhill to claim his first goal in City’s colours.
Fernando added a second before half-time, stabbing home after Myhill and Jonas Olsson got in a muddle at a corner.
Both teams hit the woodwork in the second half — Sergio Aguero and Bony in quick succession for the hosts; Saido Berahino for West Brom — before David Silva diverted in a shot from City substitute Stevan Jovetic in the 77th minute.
West Brom manager Tony Pulis expressed bewilderment over McAuley’s dismissal, saying: “How he gets the lad wrong is just absolutely amazing to me.
“The second goal shouldn’t be allowed. Fernando kicked Saido in the face while jumping and it’s a decision which leads to the second goal and kills the game.”
Victory helped City draw a line beneath last weekend’s shock 1-0 loss at struggling Burnley.
But although they are now within sight of Chelsea, Jose Mourinho’s side have two games in hand, beginning with a trip to Hull City on Sunday.
Arsenal, four points behind City in third place, visit Newcastle United later on Saturday, while fourth-place Manchester United travel to fifth-place Liverpool in a crunch clash on Sunday.
Saturday’s fixtures will also see Dick Advocaat begin his tenure as manager of relegation-threatened Sunderland with a trip to West Ham United.