The Dublin born defender started his career with Bray Wanderers before being picked up by Blackburn Rovers. He spent nearly four years with the Premier League side but never made the break through. Loan spells with Swindon and Livingstone saw him make the move to Scotland a permanent one. He played over 50 games for Livingstone before a move back to England to join up with Plymouth Argyle. He had a very successful time with Argyle and went onto play over 170 games during his four years at the club. A two year stay at Sheffield Wednesday saw him play over 51 games before the short move to join up with Rotherham United.

Simpson had been in talks with Coughlan since the end of last season and a move to join Town. The move seemed to be off at the end of June but talks had continued and Simpson finally got Coughlan's signature a week before the start of the season when he signed on a 2 year deal. His first season in amber and blue was a successful one with Cough's being made captain part way through the season.