Ferguson made his first-class debut for South Australia on 16 October 2004 against Victoria at South Australia's home ground, the Adelaide Oval, with scores of 2 and 46. In just his second match, he top-scored for South Australia with 93 in the second innings against Queensland, almost taking the Redbacks to an unlikely victory. Ferguson scored a duck in a disastrous yet memorable innings for South Australia in which they were dismantled for a record low total of 29, mainly due to a devastating spell of 7/4 from Australian representative Nathan Bracken. He scored his maiden first-class century in the second innings of the match with a score of 103. He had a very strong debut season overall, top scoring for Redbacks with 733 runs at an average of 38.57 runs per wicket. He also scored 225 at an average of 28.12 in the one-day ING Cup.