Amir Ibragimov set United on their way inside the first minute, sweeping home from a Jim Thwaites free-kick, before Jacob Watson doubled the lead ten minutes later with a neat finish from a Bendito Mantato cross. Gabriel opened his own account for the afternoon just before half-time, volleying home after Nathaniel-Junior Brown's blocked shot fell into his path, before adding two more in the closing stages to complete his hat-trick and seal the win, the last coming after he controlled a Thwaites ball over the top and rifled a finish past goalkeeper Rauf Ayyubov.
Sabah, who had no answer to United's early dominance, retreated into a deep block for long spells of the contest, limiting United to a string of long-range efforts before Gabriel's individual quality proved decisive either side of the interval.
Godwill Kukonki was forced off with an injury during the first half and replaced by Rafe McCormack, while goalkeeper Ayyubov produced several smart stops to prevent the scoreline from growing even further out of hand.
The rout came on the same day United confirmed Adam Lawrence would continue as the club's lead coach for the Under-21s, with his remit now extended across the entire Professional Development Phase spanning the Under-16s to Under-21s. Lawrence, 40, returned to Carrington in January after Travis Binnion's promotion to Michael Carrick's first-team coaching staff, and will also take charge of United's UEFA Youth League fixtures — the competition in which Gabriel's side made such a statement.
Academy director Stephen Torpey said: "I'm really pleased that Adam will lead our Professional Development Phase. Having worked for Manchester United for a number of years, Adam fully understands the football club and our ambitious plans for the future of the Academy.
"There is great alignment across the football club; the excellent working relationships will really benefit our young players as we continue to strive to be the greatest developers of football excellence."
Lawrence previously guided Manchester United's Under-18s to the national title and Premier League Cup double in 2023-24, and led last season's Under-21s to the Premier League 2 play-off final. With academy prospects such as Gabriel now progressing through the pathway he oversees, United will hope this rout of Sabah is an early sign of what the reshaped structure can produce.