Johnson suffered concussion in the draw at Blackburn and was replaced at half-time.
McLeish said: “I had to drag Roger off. You know how he never wants to stop playing. He was just saying ‘give me half-time’, but I said ‘no chance’.
“He had a bit of a rant and a rave, as he does.
“But I told him there was no way I was going to compromise the health and safety of one of my most important players.
“The doctor felt there was concussion. Roger was a bit groggy but he will get over it.
“We don’t think it’s too severe and hopefully he will get over it for the weekend.”
