Johnson admits that Saturday's 1-0 win against the club he supported as boy was an unlikely victory.
"It's the first time since I've been here that we've beaten anybody in the top six," Johnson told bcfc.com.
"We've nicked a few draws but it's the first three points.
"They were three points we probably didn't expect to get, so it stands us in got stead going into the Fulham game."
"We went into the game against Chelsea on the back of a good point up at Man City," he said. "It was always going to be difficult against the champions, who are a superb team.
"But they were under pressure coming here on the back of two losses.
"They wouldn't have fancied coming here because as we showed on Saturday our home form is superb.
"That's twice at home we've kept them out (last season's encounter at St. Andrew's finished 0-0)."