Unsurprisingly, the travelling support had been quick to point that Sunderland were playing their kids.
That was true, but it was one of Sunderland's own youngsters who sparked a second-half surge that saw the Black Cats run out comfortable winners.
Benji Kimpioka's half-time introduction brought the Black Cats to life as they ran out 4-0 winners.
Sunderland are now two games away from Wembley after battling through a difficult opening half.
It had been an evening where no one had known quite what to expect, on or off the pitch.
Neither side had been keen to hype it up too much pre-match but even with an attendance of just a shade over 16,000, there was an unmistakable edge to the atmosphere.
The game itself settled quickly into a rhythm very similar to so many League One games at the Stadium of Light this season.
Newcastle defended in numbers and challenged the hosts to break them down.
While they enjoyed most of the possession and had a couple of openings, generally Sunderland struggled to test goalkeeper Nathan Harker.
Charlie Wyke's header forced him into an early save, while Alim Ozturk went close when he fired a loose corner wide from the edge of the area.
Newcastle were generally content to defend deep, but they did have an opening when Dylan McGeouch was robbed of possession in his own box. Adam Wilson hit a low cross into a dangerous area but nobody could get a touch.
The Black Cats had the ball in the net when Bali Mumba turned a Chris Maguire cross into the far corner half an hour in, but the linesman correctly judged that the ball had first gone out of play.
Sunderland lacked the cutting edge required but began the second half at a much better tempo and quickly reaped the rewards.
Kimpioka replaced Duncan Watmore and quickly brought some vibrancy to the game.
Sunderland looked certain to open the scoring when Jerome Sinclair gathered a flick from Wyke, but the forward hit the post from a matter of yards.
Within a minute they were ahead, Chris Maguire's corner turned goalward by the unfortunate Kelland Watts.
Robbin Ruiter had to be alert to turn a deflected effort from Callum Roberts away from goal but the momentum was now all with Sunderland and they soon doubled their advantage.
Only a superb clearance prevented Maguire from scoring at the back post, but Wyke then towered above his marked to head a corner into the roof of the net.
Sunderland had control of proceedings now and made it three as the final ten minutes approached.
Sinclair made a fine run towards the box, Newcastle scrambling clear. McGeouch react quickest to spot the loose ball and played a sharp pass to Maguire, who had pulled into space on the edge of the area.
His half volley was clean and flew into the bottom corner.
Kimpioka got the goal he deserved when he bravely rose to beat Harker to high ball, nodding into an empty net and adding some gloss to the win for the hosts.
Sunderland XI: Ruiter; O'Nien, Flanagan, Ozturk, James; McGeouch (Hackett, 83), Mumba; Watmore (Kimpioka, 45), Maguire, Sinclair, Wyke (Molyneux, 76)
Subs: Stryjek, Diamond, Taylor, Hunter
Newcastle United U21s: Harker; Walters, Bailey, Watts, Gibson; Longstaff, Allan (Longelo, 68), Sangare, Wilson (Cumbreras,74), Roberts; Sorensen (Toure, 55)
Subs: McEntee, Langley
Bookings: Mumba, 41
Attendance: 16, 654 (2,780 away)