Gallardo feels like a time bomb. K/BB below 2, HR/FB nearly half of what it's been the last four years. It's only a matter of time before he starts giving up runs. If you get him for very little (like a Colabello), he's a nice little piece for the 5th spot, but I wouldn't replace someone like Estrada with him.
Gallardo shouldn't be "the move". He could be the move before the move, but unless the Jays want to keep Estrada in the rotation (which isn't exactly ridiculous), they'd need one more big arm.