As a youngster, Walker represented England at youth and schoolboy level and signed professional forms with Nottingham Forest in September 1992.
Walker was a regular with United until he moved to Lincoln City in July 2000, playing in the 1998–99 Football League Division Three play-off final win at Wembley Stadium against Leyton Orient.
Walker joined Exeter City in August 2002, but his solitary season with the Grecians ended in relegation from the Football League.
Walker achieved a possibly unique hat-trick of successive relegations out of the league by playing for York City on loan for two months in the 2003–04 season.
With six weeks of the season remaining Chester lay bottom of the League Two table and Walker seemed set for yet another relegation experience, but a late run of wins saved City from the drop.