Born in Luton, Blackett started his career at Spartan South Midlands League side Dunstable Town, before moving to Isthmian League club Arlesey Town. After only one year at Arlesey, Blackett and teammate Craig Mackail-Smith signed for Conference National side Dagenham & Redbridge at the beginning of the 2004–05 season. After two seasons of finishing with Dagenham in mid-table, Blackett played a part in the Daggers' promotion-winning campaign of 2006–07, but was sold to Peterborough United in the January transfer window, again alongside Mackail-Smith.
