[5] On 8 August 2015, Sinclair made his Football League debut in a 1–0 home defeat to Northampton Town.

[9][10] After picking up an injury which required surgery and saw him out of action for over six weeks,[11] he missed the end of the 2015–16 season, including a dramatic match against Dagenham & Redbridge on the final day, which ended in a 2–1 win, after a 92nd-minute winner earned Sinclair and the club back to back promotions.

[15] Sinclair was released when his contract expired at the end of the 2018–19 season[16] having become a strong fan-favourite during his time with the club, earning cult hero status.

[17][18] Sinclair signed for Walsall, who were newly relegated to League Two, on 21 May 2019 on a contract of undisclosed length, effective from 1 July.

[23] In 2023, during a short spell back in England, he joined Spartan South Midlands Division One club Real Bedford, managed by brother Rob.