following the sacking of simon grayson as huddersfield manager on 24 january 2013, the manager of the under-18 team, mark lillis, was promoted to the role of caretaker manager, and gave sinnott his first appearance in the huddersfield first team in their 1–1 draw against leicester city in the 4th round of the fa cup at the john smith's stadium on 26 january 2013. after the match, sinnott expressed being positive on his debut and described himself as "not really the nervous type!" his first league appearance was as a substitute in town's 6–1 defeat by nottingham forest at the city ground on 19 february 2013.