He played for a number of amateur sides as a youth but began his professional career with Clyde in the Scottish Football League.
Born in Glasgow, McLachlan began his football career at Crosshill Amateurs before spending time with junior sides Parkhead and Rutherglen Glencairn.
[3] McLachlan spent three years with the then Shawfield Stadium football club, interrupted by a short loan spell at King's Park Strollers.
[6] McLachlan made his debut for Cardiff alongside Ferguson as the attacking trio combined in a 5–2 victory over Leicester City.
He added a brace three weeks later during a 4–1 win over Blackburn Rovers, while the Daily Herald reported that "he delighted City's supporters with his fine form".
[7] Cardiff went on to win the final on 23 April 1927, defeating Arsenal 1–0 with a goal from Ferguson to become the only team from outside England to have won the competition in its history.
He played in all five of the club's matches, scoring in the sixth and seventh rounds against Ebbw Vale and Barry Town United.
[11] In the Second Division the following year, McLachlan was displaced by Fred Warren at the start of the campaign before being restored to the first team in late October 1929.
[13][14] United's local rivals Manchester City had also submitted a competing bid for McLachlan after manager Peter Hodge had attended his last match for Cardiff.
[17] During his first year with United, an injury crisis at the club led McLachlan to switch from his usual outside left position to halfback.
His performances resulted in him retaining the position on a regular basis and, at the start of the following season, he was appointed captain of the side.
[19] The Independent's assessment proved telling as United went on to finish bottom of the First Division, nine points behind their nearest rivals.
[1] In 1935, McLachlan was the successful applicant out of almost one hundred who applied for the job as manager of top division Dumfries side, Queen of the South.
[1][4] He was one of two applicants on the final shortlist, beating out Queen's Park trainer Bert Manderson who decided to remain with his side.
The surgery discovered inoperable cancer and McLachlan died in September the same year at his home in Branford, Connecticut.