Long began his career with
Oxford United and made his professional debut on 27 April 2013 as a late substitute in a 3–0 victory over
Accrington Stanley on the last day of the
2012–13 season. His first starting appearance was in a 1–1 draw with
Morecambe in League Two on 22 February 2014. On 20 November 2014, he joined Kidderminster Harriers on loan as part of a deal that saw
Chey Dunkley going the other direction. Following his return to Oxford, he scored his first goal, in a 2–3 home defeat against
Southend United in
EFL League Two on 17 January 2015. Injuries limited his appearances in
2015–16 and
2016–17, although his contract with Oxford was extended by a year in March 2017. He was loaned to
Hampton and Richmond Borough in January 2018, a loan that was later extended. Despite not having played a first-team fixture for Oxford in
2017–18, he signed a new one-year contract in June 2018. Already the club's longest-serving player, having joined the club as an 8-year-old, in June 2020 he signed a two-year extension with Oxford United. In April 2021, Long signed a further three-year deal with the club. He was voted both the Players' and Supporters Player of the Season at the end of the
2020–21 season. His contract was extended at the end of the
2024–25 season, and again in March 2026. ==Career statistics==