Blackburn Rovers scouts were reported to have been watching Mackay-Steven on 24 August 2013, in Dundee United's 4–0 victory over St Johnstone, a game in which he scored. On 12 April 2014, he scored Dundee United's second goal in a 3–1 win against Rangers in the Scottish Cup semi–final at Ibrox. In the final on 17 May, he started in the 0–2 defeat to St Johnstone at Celtic Park, being substituted for Ryan Gauld after 64 minutes.