Defender ruled out until the new year
The defender will have his second knee cartilage operation of the season, having previously undergone surgery early last month.
This new injury is unrelated to his previous problem but is another blow for boss Aidy Boothroyd.
In better news, Chris Hackett and Adebayo Akinfenwa have shaken off their midweek sickness bug and will be fit to face Wycombe on Saturday. Jake Robinson and Lee Nicholls are also back, but Louis Moult serves the final game of his 3 match ban.
“Chris has recovered from illness and Ben Harding is available,” confirmed boss Aidy Boothroyd.
“John Johnson is going in for an operation on his knee on Saturday and he will be out until January.
“Clive Platt has been carrying a bit of a back injury but the fact that he just gets on with it and plays injured tell you a lot about his character.
“People are sometimes very keen to point out what Clive can’t do instead of looking at what he can do and anyone that has played with Clive will tell you what a good player he is.
“The youth team did very well on Wednesday night to beat York 5-0 in the FA Youth Cup.
“I think the players can see with the likes of Lewis Hornby and Ivan Toney getting their chance that there is an opportunity for them here and from what I saw on Wednesday night there might be a few more players getting a crack.
“We won’t be putting any pressure on the young players that have come in and whether they can sustain their level of performance for a long league campaign is very doubtful but there might be some answers for us in the short-term.”