The Red Devils meet City at the Etihad Stadium on Thursday night in a match where the focus is usually based on local pride rather than the consequences of next season.
United sit fifth on the Premier League table, one point behind fourth-placed City, and Mourinho says the only objective for his players is to achieve a positive result so they can enhance their chances of securing Champions League football for 2017/18 by virtue of their league finish or winning the Europa League.
"It means nothing," he said.
"If we finish fifth and they finish sixth, it means nothing. If they finish third and we finish fourth, they are above us but it means a lot.
"This is not about Pep [Guardiola], this is not about City, this is about objectives and we want to try to play Champions League football. We still have two doors open."