Sadler had stints in the youth academies at Newcastle UnitedManchester United and Barnsley before joining Scottish club Gretna.

During his time at the club, Sadler was appointed reserve team manager, helping the side to win the Northumberland Senior Cup.

A short spell at Norwich City under Glenn Roeder was followed by a return to North East England, where he was assistant manager at Blyth Spartans, Team Northumbria, and Gateshead.

[2] On 26 February 2019, following the sacking of Puel, Sadler and joint-caretaker manager Mike Stowell oversaw a 2–1 home win over Brighton & Hove Albion.

[6] On 28 August 2021, Sadler joined the backroom staff of the Northern Ireland national team in conjunction with his coaching role at Leicester City.