"Joe comes in and it will be a fantastic competition between him and Maik, two great goalkeepers," the Blues boss told bcfc.com.
"He obviously hasn't come in to sit on the bench but I am not making any guarantees, it's as simple as that.
"We have to see how the lads do and how the competition affects them. I'm sure the two of them will handle it, being part of the goalkeeper's union."
McLeish added: "Joe lost his place to Shay Given last season and probably felt a little hard done by, but he got on with it, didn't hold any grudges with Shay; in fact I think the two of them are great pals.
"It's just one of these things that happen in football and you have to deal with it mentally, as well as the physical side of things."