Ferguson has been playing with a broken rib suffered in their Carling Cup final victory.
McLeish has an open mind over the theory that British players, like Ferguson, are more prepared to play when less than 100% fit than foreign stars.
He said: "I have played with players at Aberdeen and we started bringing foreigners into the team.
"They were great players but they wouldn't play if they weren't 100%. But I am not blaming the foreigners for that. They are great players and they don't take some of the chances we do.
"But maybe we are the daft ones - us Brits.
"I always remember going through it myself, playing when not 100%, and thinking 'I wish I hadn't played today' if I had a nightmare."