United Debut: v Dundee (H) 3-2 LC 11/8/62.

Signed From: Forfar Athletic 11/5/62.

Transferred to: Free Transfer 21/4/72.

After the departure of goalkeepers Ugolini and Brown, and only a 16 year-old Sandy Davie as cover, Jerry Kerr needed a more experienced keeper and brought Mackay to Tannadice. After only a handful of games into his Tannadice career, Mackay picked up an injury in a League Cup match with Celtic, which eventually ruled him out of the rest of that season. Davie took over in goal and played so well that Mackay didn't get his place back until 1964. Mackay was the first choice keeper in 1965/66 when United qualified for Europe for the first time, but lost his place to Davie again and missed out on the European ties against Barcelona and Juventus. Regaining the No.1 jersey the following season, Mackay stayed for the next three seasons, playing in the European ties against Newcastle in 1969 and Sparta Prague in 1970, and eventually left United in 1972 after losing his place to Hamish McAlpine.