Mackay-Steven, now a full Scotland internationalist, was once another of this country's talented teenagers. Plucked from Thurso as a boy by Ross County, he was eventually transplanted to Anfield, before injuries intervened to send him back north, via a short stint at Fulham. On Saturday, he thrived in Gauld's diminutive shadow. First, his cheeky scooped pass led to Stuart Armstrong's opener, then later a swish of that fearsome left boot sent the ball high into Jamie MacDonald's top corner to clinch United's sixth consecutive home win.
An expert witness on the merits and demerits of moving south, Mackay-Steven said afterwards that he had not spoken specifically to Gauld, John Souttar and co on the subject of whether uprooting to the Premier League is all it is cracked up to be. He does not envisage doing so either, so switched on and grounded the players in question appear to be.
He does think, though, that their development is best served in the SPFL Premiership at United for now, and he hopes - whatever happens -the squad remains unchanged in January to see what they can achieve.
By the end, with Brian Graham's bullet header and John Rankin's deflected shot flying in, United had scored four goals for the fourth domestic match in a row for the first time since the 1930s, and moved menacingly into third place.
"It can work out for you, or it can't," said Mackay-Steven. "There is no right or wrong answer. But I really feel that here is the right place for everybody just now.
"I haven't really spoken to them about moving or the speculation but those two at training, and the other ones who have been linked, you could never tell, because they are just really level-headed boys, who are happy to play football. It is like being in the playground every day at training."
The squad was the star of the show at Tannadice on Saturday. The efforts of Graham, a jobbing striker lately of Raith Rovers, meant that Nadir Ciftci's absence - the Turk was serving his controversial suspension for 'manhandling' assistant referee Gavin Harris during the Scottish League Cup quarter-final against Inverness Caledonian Thistle - hardly registered. Armstrong and Gauld influenced the game from midfield, Souttar showed off his range of passing from the back, unsung heroes John Rankin and Paul Paton manned the trenches, and even David Goodwillie gave the side late impetus from the bench.
"The young boys have got all the hype and rightly so, because they have been unbelievable, but we have got such a good, big squad," said Mackay-Steven. "Big Brian got his goals and slotted in really well and we have others on the bench who are more than capable of stepping into anyone's shoes if they get injured. This is the way we want to play. We don't want to stop and be comfortable - we want to keep attacking until the final whistle and score a few goals.
"This is definitely one of the best United teams I have been involved in. From a selfish point of view I hope everyone stays in January because I think we can achieve something here, we are still in the Scottish Cup and it is all to play for in the league, so I hope we can stick together."
It was not just the home players who impressed. Although Hearts have now shipped 11 goals in a week, Jamie Walker gave Mark Wilson a torrid time down Hearts' left, winning one penalty, and nearly earning another, only for Craig Thomson to book him for diving instead.
That was not Hearts' only injustice on the day. Callum Paterson felt Sean Dillon had fouled him in the run-up to United's crucial second goal, and Kevin McHattie feels the club's luck has to turn sooner or later. "I just turned round and saw Callum lying on the ground," said McHattie. "I definitely think 4-1 is harsh, a draw would have been a fair result."