Saturday's defeat at Oldham leaves them in 22nd place, and Johnson will act now to try and reverse their alarming slide.
City's boss said: "Some players are good when we lead games, but not so good when we are one or two-nil down.
"There's no professionalism, passion or pace - we need to change that and that can be done by moving people on and bringing people in.
"I've brought a few players in, but this is not a Gary Johnson side yet."