Originally from Pakenham, Victoria, he played with Gippsland Power at TAC Cup level in 2005-06, in-between completing a pre-season with Hawthorn. He showed good speed at the Victorian State Screening Session with a 20m Sprint time of 3.00sec. A good second season in the TAC Cup as a mature aged player would see him become one of few 19-year-olds drafted at the 2006 AFL Draft, selected by Collingwood in the fourth round of the draft with pick 63.
In 2007, he played four games with the reserves side in the Victorian Football League as a defender, making an impression, being emergency for the round 7 clash against Carlton, before making a surprise AFL debut against the Western Bulldogs at Telstra Dome. He impressed to keep his spot, but made a name for himself in round 12 when he played an effective containing role on Michael O'Loughlin of Sydney, and then on Hawthorn spearhead Lance Franklin a week later. He would continue to play the role, missing one game through a rest, for the rest of the season, including the final series. He once again nullified O'Loughlin in round 21, where he had 25 disposals and 8 marks, and earned an AFL Rising Star nomination.
Goldsack was recalled for the 2010 Grand Final replay, replacing Leon Davis. Goldsack kicked the first goal of the game. His mother was one of many people to have successfully bet on him kicking the first goal, despite the high odds. Artist Jamie Cooper featured the bet in the celebratory painting of the Collingwood team, with Goldsack holding a betting slip with the words "Mrs" and "80-1" written on it.