Ferguson picked up the injury in a challenge with Arsenal's Samir Nasri during the Carling Cup final nine days ago. His influence was sorely missed during Saturday's 3-1 home defeat by West Brom which pushed Blues back into the bottom three of the Barclays Premier League.
But McLeish will put no pressure on Ferguson and allow him to make his mind up on whether to go under the needle.
McLeish said: "Barry has had this before when I was at Rangers in a Scottish Cup final.
"Perhaps it was easier then, but there can be things done to alleviate it, in terms of an injection. Barry, the doctor and I were discussing it on Saturday because he hates missing matches.
"Of course, he is a key component in our games just like Cesc Fabregas is a talisman to Arsenal and Wayne Rooney for Manchester United.
"We all have key players. But I'm not going to force the player into doing it. His welfare comes first and it must come from him if he makes the decision to have the jab."
Source: PA
Source: PA