Johnson believes that the game at Ashton Gate on Saturday evening will have a major bearingon whether or not City can maintain their promotion play-off aspirations.
"I'd ask that as many people can come along to support the lads on Saturday in what is another 'cup final' for us, he told the club's official website.
"We are now into a massive part of the season and the fans will play a big part in that.
"The Ashton Gate atmosphere has been rising since the start of the season, and has grown into a crescendo as we reach the final stretch.
"That can only work in our favour and I'd like thank our loyal fans in anticipation of that support."