However, it was his fellow 17-year-old Ryan Gauld who really stole the show, with a virtuoso display involving everything from blinding pace, outrageous showmanship and a clear eye for the killer ball.
If there is any criticism of the youngster, it is that he should perhaps have got himself on the scoresheet, but that would be unnecessarily cruel. Souttar, meanwhile, a calm, elegant centre-back, barely broke sweat against the experienced Kris Boyd while Gauld, the subject of a few rather agricultural tackles as the match went on, was outstanding.
With two such talents in the sides, others such as Nadir Ciftci tend to be working under the radar right now, but his 55th minute goal was his fifth in eight appearances and he warned Gauld afterwards that rough treatment is something he may have to become accustomed to.
"He is one of the best players I've worked with and people are watching him," said Ciftci. "People know he can put strikers through and they want to stop him, which is not nice. It is Scotland and you have to put up with it."
For Kilmarnock, there was little to lift their spirits in the wake of a ninth league game without a victory other than the display of on-loan Celtic midfielder Jackson Irvine in the second half.
Chairman Michael Johnston is still being targeted by irate supporters, but his managerial namesake Allan is not far away from attracting similarly unwelcome attention. Certainly, the jeers from the away end were very evident when referee Willie Collum blew the final whistle.
With United having replaced Keith Watson with Gavin Gunning in the early stages after a collision with David Silva had left him with a gashed head, David Goodwillie passed up the first of a handful of opportunities just after the half-hour.
Getting involved in a free-flowing move that featured Stuart Armstrong and Andrew Robertson, he laid the ball off to Gauld and showed fine reading of the game to move on to a terrifically-weighted return pass.
Goodwillie drew the keeper well, but blotted his copybook by sending his shot off Craig Samson's left-hand post.
The former Scotland striker then missed another fine opportunity along with Gauld at the start of the second half, with visiting players Ismael Bouzid and Manual Pascali arguing with each other over a blunder that gave Ciftci an opening only denied by a block from Darren Barr. Perhaps still distracted by their fury, both failed miserably in preventing the former Portsmouth forward from securing the points.
Goodwillie, having moved on to an Armstrong pass wide left, picked out Ciftci around 20 yards out with a looping cross and his low first-time volley went straight through Samson and into the net.
Even so, keeper Radoslaw Cierzniak had to intervene on 76 minutes to push wide a header from substitute Irvine after he had connected with a Sammy Clingan free kick and made a brilliant save from a long-range shot from the Australian in stoppage-time.