He started his professional career with Motherwell in 1984,[4] helping the club to gain promotion before moving to Celtic in the summer of 1987 for a fee of £350,000.
At Bolton, Walker returned to his form of 1988, establishing a prolific partnership with John McGinlay[6] as the Lancashire side earned promotion to the First Division in 1992–93.
[9] Due to the arrival of Andreas Thom in the summer of 1995, Walker was again deemed surplus to requirements at Parkhead and joined Sheffield United for £500,000 in early 1996.
Nevertheless, Walker was again to quickly fall from favour, and after brief loan spells at Hibernian (where he scored in an Edinburgh Derby), and Raith Rovers in 1998, he ended his career in the lower leagues.
Since his playing retirement, Walker has worked as a pundit for STV on their Scotsport highlights programme, which he became the main presenter of, alongside Grant Stott, due to Jim Delahunt's departure.