"I know we don't have that time, we have to get him into action a lot sooner.
"It's just letting him get a feel for things, a feel for the pace and for him to see for himself and also motivate himself to believe he can make a difference when he gets out there."
Zarate's low centre of gravity and busy, elusive dribbling style brings something different to the table.
"It would be nice to think we could throw him straight in and we'd get a brilliant return," McLeish added.
"But it isn't as simple as that.
"He's is a talented player, no doubt, but the main thing we are looking for from him is an end product."