[1] He grew up in the suburb of Johnsonville[2] and attended Wellington College, before moving to the United States for his senior year of high school.
[3] As a freshman at San Jacinto College in 2008–09, Prewster averaged 8.9 points, 9.0 rebounds and 1.8 blocks per game in helping the basketball team to a 25–5 record and the ETJCC South Division title.
As a sophomore in 2009–10, he earned first-team All-ETJCC and All-Region XIV honors after averaging 14.3 points, 11.8 rebounds, 3.0 assists and 2.0 blocks per game.
[8] For the 2011–12 season, Prewster decided against returning to the United States and instead signed with the New Zealand Breakers of the Australian NBL.
[7] He returned to the Wellington Saints in 2014[12] and averaged 8.7 points, 4.0 rebounds and 1.3 assists in 20 games,[7] while winning his second New Zealand NBL championship.
[27] In February 2020, Prewster signed with the Wellington Saints for the 2020 New Zealand NBL season, returning to the franchise for a third stint.
[31][32][33] The Saints' semi-final against the Auckland Huskies on 22 July 2021, Prewster recorded 12 points, 10 rebounds and 10 assists in a 99–73 win.
[37] Prewster captained the Junior Tall Blacks at the 2009 FIBA Under-19 World Championship, where he averaged 10.4 points, 6.6. rebounds and 1.2 assists per game.
[2] He made his FIBA Oceania Championship debut on 18 August in Game 2 of their two-game series loss to Australia, appearing in the final 29 seconds of the match.
[39] In February 2020, Prewster played for the Tall Blacks against Guam in the 2021 FIBA Asia Cup qualifiers.