Mourinho dismissed the suggestion experience had trumped certain players, citing substitute Marcus Rashford's ebullience, and added some players would not be considered for selection in future games against eminent opponents.
"It has nothing to do with experience or age because you have the kid then in the second-half and the kid looked like he was playing in the Under-18s versus Salford City," Mourinho said.
"So it's about the individual and every individual reacts to the dimension in different ways, so it's difficult to predict.
"It only gets easier when you know the players very, very well. When you work with them one month, two months, three months, four months, you see how they react in certain circumstances, you try to get a better feeling.
"So maybe in the next big game in the Premier League probably I know who can accept well the dimension of the game, which is very important."