Born in Glasgow, McLachlan began his football career at Crosshill Amateurs before joining Celtic as a junior but stayed for only two weeks before joining Clyde. McLachlan joined Clyde and spent three years with the then Shawfield Stadiumfootball club, interrupted by a short loan spell at King's Park Strollers. McLachlan, a speedy left winger, was then transferred in November 1925 for a fee of £2,000. He joined the strongest Cardiff City side in the club's history. Promoted to the top division in 1921, they had finished runners up in the 1923-24 League Championship and in the 1924-25 FA Cup. Fellow Scot Hughie Ferguson also joined in 1925. Many Football League clubs were interested in signing McLachlan but he was persuaded to join City as his father was captain of a ship that regularly called at Cardiff docks. Much to McLachlan's disappointment he missed out on an international cap in 1926 with a broken leg picked up against Leicester City. The high point of McLachlan's career came with Cardiff City when he was part of their victory in the 1927 FA Cup Final. McLachlan recovered from the broken leg in 1926 to star in Cardiff's FA Cup triumph. At Cardiff, McLachlan moved from outside left to wing half. He played 139 league games, hitting 22 goals. While at Cardiff, in 1928, he played for the Anglo-Scots against the Home-Scots in an international trial match at Firhill. He left the Bluebirds in December 1929 for top division Manchester United, where he captained the side between the departure of Jack Wilson in 1932 and the appointment of Louis Page as captain. McLachlan scored four goals in 116 games for the Red Devils. In June 1933, McLachlan was appointed as a player-coach at Football League newcomers Chester, who were about to embark on only their third Football League season. Throughout the 1930s, Chester never finished outside of the top ten in Division Three North; their lowest finish came in 1933–34, when they came in 10th place.
Managerial career
McLachlan had a spell as player-manager with French side Le Havre in 1934–35. He was offered a further contract with the club, but his ambition was to manage a Scottish First Division side. 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. His appointment was announced on 29 June. He was manager of one of the landmark events in the history of Queen of the South; the 11-game 1936 overseas tour and the Algiers invitational tournament. Queens returned with the trophy after beating Racing Santander in the final. Players at the club during this time included Willie Fotheringham, Willie Savage, Willie Culbert, Willie Ferguson, Joe Tulip and Irish international Laurie Cumming. McLachlan's time at Queens was part of a long spell the club spent in Scotland's top division. It was under McLachlan that Jackie Oakes first joined Queens. On 22 March, with five games remaining of the 1936–37 season, the Queens board announced that McLachlan would be leaving the club on 30 March. The week was intended to allow the outgoing manager to offer advice on team building for the next season. Willie Ferguson was named as McLachlan's successor.
