Jose Mourinho's only loss to United as manager of both Porto and Chelsea came in this fixture last season when a flukey first half Darren Fletcher header won the game for Alex Ferguson's side.
McGill advised against putting children on the filed who are not physically and emotionally to perform headers, or else there will be injuries such as concussions.
After the restart, China replaced star striker Wang Shuang with Zhang Linyan, who levelled the game 2-2 in the 72nd minute with a header four minutes after Tang Jiali's penalty cut the deficit to 1-2.