Joking aside, Trevor Sinclair is a racist half wit. Literally a half wit. Why he still gets paid to give his inane opinions, even by dross like talksport, beggars belief. His opinion does not equal "growing demand".
Ignoring who brought it up though, come on, how would you rule on what constitutes a weakened side? Everyone who played is registered in United's squad. Everyone who played for City against Chelsea is registered in their squad.
If anyone tried to rule that one player is a first team player and another isn't, that goes against the whole point of having a squad of more than 11 players, of having substitutes, of having young players and youth teams that promote into the senior sides, of having any concept of form, and a total disregard to player wellbeing and health. It would be laughed out at any level of debate.
Also the first eleven today had an average age of 25.