But Johnson believes they can pick up three points against a Blades side that are down in 14th place after just one win in nine Championship games.
Johnson told the club's official website: "I'm surprised to see Sheffield United in the position that they are (Kevin Blackwell) does seem to use the loan system extensively. When one player goes down with an injury he brings two more in.
"We all get injuries but if you lose a few games sometimes you can use that as an excuse, even with loan players. I think they've got a decent team, but then I think we have too and it's up to us to show what we can do on the day.
"We can make their situation even worse for them by showing Ashton Gate is a very difficult place to come and get a result."