Their rise up the table is down to a run of five wins and a draw from their last six games, but Johnson is refusing to get complacent.
"The dressing room is happy with the run but not elated. If we were 10 points clear at the top on the back of that run then we would be, but we still have plenty of work to do," Johnson told the club's official website.
"We knew we needed not just a good run but a massive run to get into the play-offs. We're not on that sort of run yet, but we can be as we've got ourselves going.
"It will be a good game because Norwich still need a massive three points with the relegation zone just below them, and we need three points to take us closer to the play-offs."