The Bati thrashed the United States 58-12 in their tournament opener last weekend and face a Welsh team on Sunday that conceded 50 points against Papua New Guinea in Port Moresby.
Despite scoring 11 tries, Potter said Fiji let in a couple that were preventable.
"We were just a little bit quick in our defence - we didn't make effective tackles and they probably could have had another try as well, just a guys stepped from outside the field of play to catch a ball," he said.
