Long was drafted by the St Kilda Football Club with their first selection and twenty-fifth overall in the 2016 national draft.[8] He made his debut in the fourteen point win against Collingwood at Etihad Stadium in round four of the 2017 season.[9] Long was nominated for the AFL Rising Star for his performance in the draw against Greater Western Sydney at Etihad Stadium in round five of the 2018 AFL season, during which he recorded fifteen disposals, eight tackles, four marks and a goal.[10] In the final game of St Kilda's 2022 season, Long compiled a career-best performance against the Sydney Swans which included 27 disposals, 17 marks, 13 intercepts and one goal with a disposal efficiency of 96 per cent on his 25th birthday.[11]
Long subsequently requested a trade to Gold Coast, and was traded on 5 October 2022.[12]
^The 2020 season was played with 17 home-and-away matches per team (down from 22) and 16-minute quarters with time on (down from 20-minute quarters with time on) due to the impact of the COVID-19 pandemic.