The 31-year-old former Yeovil and Bristol Rovers midfielder made 13 appearances for Kilmarnock this season before leaving the Scottish Premier League outfit in January.
Johnson's subsequent appointment at Boundary Park made him the youngest manager in English football.
Although he believes his competitive playing days to be behind him, Johnson is considering turning out for Oldham's reserve against Bury at Radcliffe Borough on Wednesday in order to run the rule over some of the youngsters whose futures are in the balance this summer.
"It is more of a tool to help the young players," he told Oldham's official website.
"I have decisions to make about two or three youngsters and by playing it will help my level of understanding of them and also their fitness."
First, Johnson leads Oldham at Preston on Tuesday night and he insists the prospects of a more hands-on role would be grim for all concerned.
"If there was a flu epidemic and I had to play, I could only manage 60 minutes at the moment," he added.