"We are delighted to get him, he has a good scoring record, he is a good footballer, he is a national hero in New Zealand and hopefully he will be a local hero in Aberdeen," the former Scotland manager said.
"What Rory brings is an extra provision and I want to emphasise that I am not in any way displeased with the strikers we have got.
"We haven't been scoring but I am convinced that the ones that we have will score goals.
"If you only have four strikers you have less than any other club in the SPL, every club has at least five or six forward players.
"He is not a replacement for Mackie, Vernon or any of the others, he is here to support the striking provision we need and there is now good competition for the positions for a start."