[4] He previously played for Dundee, Greenock Morton, Morecambe, Luton Town, York City, Östersund, Forest Green Rovers, Southport, Barrow, Chorley and Workington.

[7] He signed for the Scottish Premier League team's youth system on a two-year scholarship straight from school after playing three games on trial.

[19] Barrow faced Conference Premier champions Stevenage Borough in the Final on 8 May 2010 and Walker scored the winning goal with a 25-yard "wonder strike" in a 2–1 victory after extra time.

[20][21] Walker signed for fellow Conference Premier side Luton Town on 17 November 2010, initially on loan, with a view to a permanent transfer in January 2011.

[22] He scored on his Luton debut with a header from Matthew Barnes-Homer's cross and earlier in the match assisted a Jake Howells goal in a 5–1 win at home to Histon on 20 November 2010.

[30] Walker was handed a three-match suspension after being red carded during a 0–0 draw away at former club Barrow on 19 November 2011 for a tackle on Jason Owen during stoppage time.

[34] After converting Jonathan Smith's header, his first goal of the season came in the following game, a 3–1 defeat at home to Wycombe Wanderers on 18 August 2012, which was York's first Football League fixture since their promotion.

[3] After making two appearances for Forest Green, Walker signed for Conference Premier rivals Southport on 27 February 2014, on a loan deal until 26 March.

[43] He started the game alongside Barrow teammate Paul Brown, with England winning the match 4–0, although he was substituted at half time for Adam Boyes.