On-loan Watford midfielder Walker lasted just 39 minutes of the latest 1-1 draw at Hereford in midweek before going off with a hamstring injury and is out.
Defender Tozer missed out altogether in midweek after injuring his hamstring last weekend while striker McKenzie continues to be a doubt with a thigh injury.
However, midfielder Abdul Osman is available again after completing a three-match ban, but striker Shaun Harrad serves the second of his three-game suspension.
Manager Ian Sampson said: "Josh, Ben and Leon are probably all going to be out of the game on Saturday so we will have to reshuffle the pack a little bit.
"John Johnson slotted in really well at centre-half at Hereford and defensively Paul Rodgers did an excellent job at right-back after coming in."
Source: PA
Source: PA