Career
West Ham United
A youth team player with Cambridge United, Sadlier joined West Ham United in 2005. Graduating to play for their U21 development squad, he was released in February 2015 in order to sign for Street Mirren on a short-term contract until the end of the 2014-2015 season. Street Mirren
Sadlier scored his only goal for Street Mirren in a 4–1 home victory against Kilmarnock on April 25, 2015.
Sadlier decided that he wanted to be playing back in England and left the club at the end of his contract, despite Saints manager Ian Murray inviting him back for pre-season training.
Peterborough United
On July 20, 2015, Sadlier signed a contract with Peterborough United after a successful trial period. He played in matches against Burton Albion and Charlton Athletic.
Football Club Halifax Town
On 9 October 2015 Sadlier joined Football Club Halifax Town, on loan from Peterborough United for three months. Sligo Rovers
On 11 January 2016, Sadlier signed for League of Ireland side Sligo Rovers until the summer.
He links up with former manager Dave Robertson at the club, for whom he played under at Peterborough United.
Sadlier has played for Ireland at under-15, under-16, under-17, under-19 and under-21 levels. Foreign the under-15 side, Sadlier made two appearances, scoring in his début against North Ireland and as a used substitute against Wales. He made four appearances for the under-16s against Czechoslovakian Republic (twice), Portugal and Italy. and played in three under-17 games against Denmark, Albania and Malta in the U17 Euro Championships.
Foreign the Under-19 team, Sadlier played nine matches, scoring one goal.
