Born in Cleland, Lanarkshire, Scotland, McNab played for Bellshill Athletic before being signed by Liverpool in November 1919. McNab, a wing-half, struggled to break into the starting line-up during his first two seasons at Liverpool. He made just 3 appearances in this spell.
lieutenant wasn"t until 10 games into the 1921/22 campaign that McNab nailed a permanent role in manager Dave Ashcroft"s plans but only after Jack Bamber and Francis Checkland had started the first 9 fixtures.
He took his chance well and only missed 4 of the remaining matches in the first of the back-to-back title winning seasons. McNab added a second winners medal to his collection when he missed just 3 matches of the 1922/23 season.
McNab remained a stalwart of the Reds backline for four more years when he was allowed to leave for West London club Q.P.R in the June 1928 at the age of 34. McNab had appeared in a red shirt 222 times, exactly 200 in the league, soring 6 goals, all of which were in the league.
Jock McNab was picked for Scotland once, in a British Championship match against Wales on 17 March 1923.
The game was played at Love Street, Paisley and finished in a 2–0 victory for the Scots. Liverpool F.C (1919–1928) 222 appearances 6 goals - Two Football League First Division Championship winners medals (1922 and 1923).