As the Canadian goalkeeper starts the treatment, John admits: "It will be tough for him but he is over the worst."
And he stresses: "Craig is in the clear as far as his cancer is concerned; it's just a case of having an insurance dose of chemotherapy, which basically gives him a little bit of a zap, so if there is anything sitting around it kills it off for good."
And he says he is happy with the swift diagnosis of Craig's testicular cancer, which resulted in his immediate operation last month.
"As soon as there was a problem with Craig the natural response was to have a scan and see what we were dealing with.
"There is no beating about the bush with these lads; you just have to get straight to the problem."
John, one of the most respected physios in the game, says there is never any penny pinching when it comes to the medical side of the club's obligations.
"We have said it over and over again about this club, people will criticise us for not spending this or that in different areas, but people who are in the know and who actually work in the club are aware that there is no expense spared or any time wasted on the players' injuries.
"They see whoever they have to, whenever and wherever is appropriate."