Johnson said: "I think chopping and changing managers isn't the way to go forward - for any team. Nobody is thinking about relegation and Alex's future - and they shouldn't be.
"It was quite difficult for him when he came in. The transfer window was just about to open, he was trying to assess the squad and was working with someone else's budget.
"He was also trying to get his own ideas across and I thought he handled everything well. Alex needs to be given time. It is no good for anybody if things change again."
The Northern Ireland international added: "I'm sure Alex will love the summer when he can really get his teeth into things seriously. He might think he needs to make wholesale changes, he might not, but I'm sure he will want to do a few things."