John Walker and Tom Robertson signed for Liverpool from Edinburgh club Hearts at the end of the 1897/98 season. Walker had been a tremendous success at Hearts, winning the Scottish League in 1895 and 1897 and the Scottish cup in 1896 which he lifted as captain. He had also made his Scotland debut against Ireland on 30 March 1895, scoring twice in a 3-1 win. In his first full season at Liverpool Walker missed just two league and cup games, scoring 11 times in 32 first division matches as the Reds finished runners-up to Aston Villa. Walker did get into trouble in November 1898 along with teammates Hugh Morgan and George Allan when they were charged with a breach of the peace and obstructing the police. They were being a little too lively on the street and a constable arrived to settle down matters. Walker shouted: ‘Let’s show him some Scotch blood!’ In the end the constable took Allan into custody while Morgan and Walker tried to prevent his arrest.

The inside-right started the following campaign in great form, scoring seven goals in the opening ten games, but only got three goals in the remaining 21. Despite the fact that Walker's goals dried up he continued to be a key player for the Reds who now relied on the goalscoring talents of centre-forward, Sam Raybould. Liverpool's last game of the 1900/01 season was against relegation-doomed West Bromwich Albion and their first League title was a realistic possibility. Liverpool had only been in first place on the opening day of the campaign but now a draw sufficed for the Reds to topple Sunderland who were equal on points with superior goal average, but had already played all their games. Walker was the hero of the day scoring the deciding goal in the first half as the Daily Express reported: "Robertson only just missed scoring for Liverpool and at the other end Garfield was charged off the ball just when about to shoot at an almost open goal. At last, however, Liverpool got away and Walker scored." The Scotsman played one more season for Liverpool before returning to his native Scotland to play for Rangers.

Johnny later emigrated to Canada with his sister and his brother, Tammy. On the outbreak of the First World War, Johnny and his brother enlisted in the Canadian army and came back to Europe and fought against the Germans. Miraculously they both survived the entire war and eventually went back to Canada.

Johnny lived on a farm in Louise, Manitoba with his sister, Lilias. Unfortunately in 1937, Johnny was involved in a tragic accident on the farm and died from his injuries.