The 20-year-old, who has yet to start a game for the Warriors in the RaboDirect PRO12, joined up with the squad last weekend after making his way from New Zealand where he was midway through a scholarship programme.
Ashe is the only new cap in the starting XV that will take on the Springboks in Port Elizabeth but is one of four changes from the team that beat Argentina last time out.
But despite his inexperience, Cotter is confident Ashe will be ready for the big occasion.
"He has been identified as a talent, that is why he was in New Zealand on that scholarship," he said.
"He has been plying his trade in Canterbury and I think they are pretty good judges of quality and character down there and he has come back with positive feedback on what he has been doing.
"Added to what I have seen in the last couple of days I think he is a talented young player. These days 20 to 21 is not old to be playing top level footie, it is now you want to be putting your hand up and saying 'this is what I want to do'.
"He is a specialist number eight and we did not have one and we want to have a look at him."
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