Born in Rotherham, West Riding of Yorkshire, Walker played as a trialist in York City's youth and reserve teams in 1976, after which he moved to New Zealand to play for Gisborne City in 1980 after being spotted playing in English non-Leaguefootball for Retford Town and Matlock Town by Kevin Fallon. After the end of the season, he returned to play in England for Football League side Barnsley in November 1980. He scored 12 times in 24 games for Barnsley, with an additional five goals in 12 games while on loan at Doncaster Rovers from February 1983, before returning to New Zealand to play for Gisborne City. Walker reached the final of the Chatham Cup in 1983 with Gisborne. He scored twice, but the match ended 2–2, and was won by Gisborne's opponents Mount Wellington 2–0 in the replay. During the 1983 season, he scored seven goals in 12 appearances. He scored 16 goals in 22 appearances and won the country's Player of the Year award in 1984. He then scored 15 goals in 22 appearances in 1985. Overall, he was the top scorer in New Zealand during three of the five years he spent playing in the country. In November 1985, Walker returned to Doncaster Rovers on non-contract terms, playing five times before moving to Cambridge United in January 1986. He scored once in 3 games, but was released by Cambridge and returned to Matlock Town. From there he joined Harworth Colliery Institute from where he was signed by Sheffield Wednesday in August 1986. He joined Darlington on loan in December 1986, where he made seven appearances, and Torquay United on loan in October 1987, where he made three appearances. He left Sheffield Wednesday having played just two league games and after scoring a hat-trick in a League Cup tie, a 7–0 victory against Stockport County, which Wednesday won 10–0 on aggregate. He then returned to New Zealand for a final spell with Gisborne City, where he took over as player-manager, but left because of financial problems at the club. He also worked as striker-coach at the club. After returning to England for a run-out with Doncaster, he suffered a cruciate ligament injury to his knee which brought an end to his playing career.
Walker spent three-and-a-half-years after his playing career ended as manager of Maltby Miners Welfare, whom he took from the Northern Counties East Football League Division One to the Premier Division. He won the Presidents' Cup in his final season in charge. He had coaching appointments with Barnsley, where he held a variety of different positions from youth team coach to assistant manager. Walker left Barnsley, along with manager Glyn Hodges, in July 2003. He soon found employment at the Leeds United youth academy in addition to work at Rotherham R.U.F.C. and undertaking scouting assignments for lower league clubs while trying "to earn enough to pay the mortgage". Billy McEwan appointed him as first team coach at York City on 28 May 2005, stating that Walker would "bring honesty and commitment to the club, as well as a lot of knowledge". He took over as caretaker manager at York on 19 November 2007, following McEwan's sacking by the club. His first game in charge finished as a 2–1 victory against Weymouth and after achieving five wins and a draw in six games, he was appointed as the club's permanent manager on 26 December 2007. He won the Conference Nationalmanager of the month award for December 2007, when the team gained 10 out of a possible 12 points in the league and made progress in the FA Trophy and Conference League Cup. He led the team to a 14th place finish in the Conference in the 2007–08 season, and also reached the semi-final of the FA Trophy and the fifth round of the Conference League Cup. During York's 1–0 defeat to Mansfield Town in an FA Cupfourth qualifying round replay in October 2008, Walker was targeted by some fans chanting his name. He was sacked as York manager on 21 November 2008. Walker joined Forest Green Rovers as assistant manager to caretaker manager David Brown in August 2009. Walker left Forest Green in September after the club appointed Dave Hockaday as their new manager. He later joined Doncaster, who he played for during his playing career, as Centre of Excellence technical development officer.
