A substitute at the interval for Oscar, Loftus-Cheek received possession just inside the Chelsea half before using a devastating explosion of pace to run free of the entire opposing midfield.
Any fans who were still dozing after their half-time pie were shocked back into life. Chelsea were leading 1-0, but their young addition wasn't settling for it. He sniffed blood and wanted some of the action.
Eventually that pattern of play fizzled out and Chelsea surrendered possession to Scunthorpe. A goal wasn't the important outcome in that moment, however. That would come later.
What we witnessed instead was a player wanting to make his mark on the game and this Chelsea team.
Loftus-Cheek had the look of caged beast who had experienced enough of his time in captivity, being locked away from public view. He was being given the opportunity to stretch his legs for once and wasn't going to deny himself that chance.
It was exciting to watch Loftus-Cheek inject some life into an otherwise pedestrian cup tie. Chelsea had been in control for much of the first half, and the danger was that the game was already over.
Scunthorpe themselves reacted and offered some threat, but any hope of a comeback was snatched from them when Loftus-Cheek doubled Chelsea's lead at 68 minutes.
"It was a really nice moment," Loftus-Cheek told the BT Sport cameras at full-time. "My first goal, so I'm really happy with that. But just to come on and play 45 minutes is amazing. I'm just happy to come on and help the team."
You could almost hear the frustration in his words. Loftus-Cheek seemed happier with the run-out than he did his actual goal.
"It was a real battle. They came here with massive motivation to beat us and we had to match that. We knew if we could match that our quality would come through, and it did."
Loftus-Cheek will remember his goal as being a big moment in his Chelsea career, ticking off another milestone as he progresses.
Hopefully it will mark something more significant, though. Hopefully it was the moment when Chelsea matured as a club.
We need to keep things in perspective. It was Scunthorpe United—a League 1 side—but Loftus-Cheek did what few young players have done in a Chelsea shirt by impacting a game when it actually mattered.
The visitors were proving pluckier than the first half suggested they would be and the longer the game stayed at 1-0, the threat of a draw or, worse still, an upset, was always there.
Arriving late into the box to tuck home, Loftus-Cheek ended that. Chelsea's 19-year-old put his experienced team-mates at ease.
@garryhayes Yep, totally agree. Minutes on the pitch don't count for much when the other team has given up. Great experience for him— Liam Twomey (@liam_twomey) January 10, 2016
That says a lot. It tells us he's a player with those capabilities—a player who can prove a game-changer for Chelsea.
Also speaking to BT Sport, Guus Hiddink seemed to suggest he was of the same opinion.
"I know these youngsters now after three or four weeks. I know their abilities and when it's a possibility, I don't hesitate to play them," said Chelsea's interim boss.
"[Loftus-Cheek] can be of big value now. He's 19, but I thought he was 22 or 23 when I came in. He has the physique of a grown player already, but he's only 19. We have to be careful, but I said 'OK, let's give [the young players] a try' and it will happen more."
Hiddink needs to be true to his word, as Chelsea's future rests on it.
Winger Kenedy, 19, and midfielder Bertrand Traore, 20, were also used as substitutes Sunday. While the latter played just seven minutes, Kenedy's appearance after 72 minutes gave him more time to impress.
We saw what we have whenever he has appeared this season. Kenedy had the same adventure as Loftus-Cheek and asked questions of the Scunthorpe defence.
He was penetrating, always probing for gaps that he could exploit to make a difference.
Chelsea fans may not have got the young line-up they were hoping for in this cup tie, but the taster was still good enough.
Hiddink's mandate is much different in his second spell at Chelsea.
Back in 2009, he had silverware to chase and a top-four finish. He delivered on all fronts, handing Carlo Ancelotti a team that was ready to fight for the league title once more.
Now Hiddink must deliver his permanent replacement this summer a team that's brimming with youth. He needs to nurture the next generation and give it time to build its experience with 2016-17 in mind.
It has been Chelsea's biggest challenge this past decade. For all the success they've enjoyed, the club has failed its young talent. There simply hasn't been a strong enough desire to bring them through, regardless of the trophies they have won.
But this generation is refusing to go unnoticed. Loftus-Cheek is the flag bearer, and he showed just why against Scunthorpe.
Chelsea's season has picked up in recent weeks, but we're still sifting through the wreckage, attempting to salvage something.
Hiddink must allow that to be the emergence of these supremely talented youngsters. Sunday confirmed they can't continue to go ignored.