McNab began his career with Greenock Morton in 1914,[2] playing nine seasons with the team until his departure for the United States in 1924.

He considered this excessively low, but when he asked for a transfer, the club placed a prohibitively high fee on him to force him to stay in Greenock.

By that time, McNab was partnered on Boston's front line with Billy Gonsalves and Bill McPherson, forming what was known as the "golden triangle".

[4] In 1928, McNab left Boston for the Fall River Over the next three season, the 'Marksmen' took three league titles as well as the 1930 and 1931 National Challenge Cups.

[6] However, McNab broke his arm the day before the decisive game and Fall River was forced to play with ten men as they had failed to bring substitutes to Chicago.

In December 1937, McNab gained his release from South Side and signed with St. Matthew's of the SLSL, playing the 1937–1938 season with them.

He immediately proved he was as good a coach as a player, taking SBF to two consecutive league and National Challenge Cup titles.

[1] The National Soccer Hall of Fame inducted McNab in 2005 as part of a process of recognising significant pre-1950s players.

In order to correct these oversights we established a Blue Ribbon panel consisting of historians Colin Jose, Roger Allaway and Hall of Famer Walter Bahr, to review the credentials of all Veterans from the pre-NASL era.