City, now on 84 points in the league table, will be confirmed champions if they beat United who are second on 68 points.
City were also shaky in the 3-0 defeat at Liverpool in the Champions League first leg last Wednesday and Guardiola is conscious that their aim to progress to the semi-finals has been made more hard after the scars of the past week. If that's so I will have to recognise that I'm not good enough or the way we want to play is not able to do that. "Obviously you can have 10, 15 minutes where the opponent is good, but in that situation we conceded three goals and that is tough against a good team but after that we go, we try it, and we could not win", Guardiola explained to the BBC.
And on his team's 3-0 defeat against Liverpool in the Champions League, the former Barcelona manager said: "Wednesday was a tough result, so hard, but we're going to try. We needed one goal and we couldn't score it", he said.
Guardiola is concerned at the rapid way City have collapsed in their last two games and forced him re-assess his philosophy. When this happens it's so complicated to win the games.
"In football anything can happen, it's the first time we've lost two games in a row this season and now we have to recover and try again, go back to the basics and win games".
"They're nearly qualified but we have 90 minutes". We could be better but we could be worse.
Having endured a disappointing first season with City, Guardiola has silenced the critics who claimed his purist principles would not work in the cut-throat Premier League, meshing his desire for a smooth passing style with an ability to compete physically.
Guardiola will know that an injury to the likes of Kevin De Bruyne or David Silva would seriously harm their chances of a Champions League turnaround.
"Of course we are sad for ourselves, for our fans - but we still have 13 points advantage and goal difference. And we didn't close it".
"We are going into it to win it".
"My motivation is to finish second", said the Portuguese, who confirmed that defenders Phil Jones and Daley Blind have returned to training, leaving goalkeeper Sergio Romero as the only player on the sidelines.