United were the last team to win a Premier League game at the Etihad Stadium and, despite a mixed start to the season, will head there full of confidence after fighting back against Bournemouth and Juventus to win both games 2-1.
Victory over Guardiola’s side would cut the gap at the top to six points but Mourinho refused to say the derby is a chance for his team to get back into the title race.
“If we draw [the gap] is nine points if we lose it is 12,” he said. “I don’t think it is the way to look at the match.
“We have to just think about the match, it is difficult enough by an isolated event.
“I want to play it as an isolated match. A difficult match against a difficult team but they think it is a difficult match for them.”
Mourinho also said that Romelu Lukaku is in line to feature for United against City if he can prove his fitness over the next 48 hours.
The striker has missed the last two games with a muscle problem but has returned to training and could be included in the squad for Sunday’s derby.
“Lukaku is training with the team [on Friday], if this answer is positive and we have of course one more session [on Saturday],” Mourinho said.
“If the answer is positive, he’s ready but in this moment I can only say he trains with the team, I don’t know his answer.”