"I know why the fans reacted as Rob is our top scorer and they felt he might get a goal," Robson said after the 1-1 draw at Eastlands.
"But it was about keeping it tight and then in the last ten minutes putting on Rob when he was fresh.
"If we had changed things too early, especially as we only had ten men, City would have opened us up and probably scored more goals.
"We've not had many breaks since I came here and hopefully we'll now get some."