Man Utd were well-beaten by Chivas in the SuperCupNI Globe Final.
Goals from Kyle Wych and Teden Mengi secured a comfortable 3-0 win at stadium:mk in front of 3,000 people.
United are in Group C with Maiden City, Seattle Sounders, Crystal Palace and Nottingham Forest.
The Reds beat FC Porto B 5-1 in a quarter-final but were knocked out by eventual winners Liverpool.
Full squad list and schedule for Man United under-14s' Copa Mallorca 2017.