The Red Devils currently lead the table by three points, but if they were to lose to their local rivals in their eagerly anticipated clash on Monday they would surrender top spot to them.
And the Frenchman is adamant that he and his teammates must halt Roberto Mancini’s side before they become too powerful.
"Beware. If City start winning it will be hard to stop them," he told reporters. "We have to stop them before they start, because they can go far. That’s how a big team starts, the first trophy they win."
"They won the FA Cup last year and if they win the league they’ll get too much confidence.
"If they win the Premier League, a page is turned and it’s a revolution, and revolutions have always been about Manchester United."
Evra feels the onus is on him and United’s experienced players to step forward and lead from the front in Monday’s clash at the Etihad Stadium.
The 30-year-old believes if Sir Alex Ferguson’s side was to prevail and win its 20th top flight title, it would be the most satisfying win to date.
He added: "If you play for Manchester United, if you’re a leader or a captain, it’s to play in a match like this. You have to accept your responsibility.
"Whether it’s me, or someone like Ryan Giggs, if you ask them which title they will appreciate the most, it will be this one."