The winger, just 14 years, 10 months and 10 days old, made his debut in the 2-1 win over Valencia - and is also believed to be the youngest player the Reds have fielded in an official youth team league or cup match.
He beat the previous UEFA Youth League mark of Benfica goalkeeper Mile Svilar, who in turn succeeded Real Madrid Iker Casillas as the youngest to appear in the Champions League.
United manager Nicky Butt, who also named 15-year-old Will Fish on the bench for the Under-19s contest, sent on Shoretire for the final 15 minutes of Wednesday afternoon's clash to replace Nishan Burkart.