Manchester United midfielder Ander Herrera labelled his side's derby clash against City as the "game of the season".
Ahead of their trip to the Etihad Stadium on Thursday, United are fifth - a point and place behind their rivals as the race for a top-four finish intensifies.
Herrera, 27, talked up the importance of the encounter, saying it could be decisive for his team, who are unbeaten in 23 league matches.
"It's going to be the game of the season," he said.
"We are one point behind them and if we win, we have the chance to finish in the top four, but if they win, it will be very difficult for us.
"I don't know the 'winner takes all' expression but it's going to be a massive game. If one of us wins it, we are not going to lose a lot of games or make mistakes after that. It will be key.
"We are in a very good moment, on a very good run and we respect them, but we are doing a lot of good things and we have to show it on Thursday."
United's busy period continues with a derby clash, followed by hosting Swansea City and a trip to Celta Vigo for the first leg of their Europa League semi-final.
Herrera is looking forward to the last-four tie, having been part of the Athletic Bilbao side beaten by Atletico Madrid in the 2012 final.
"We also have the Europa League, which is a competition that makes me very excited because I lost the final three or four years ago and I want to take that knife from my back," he said.
"So hopefully we can fight for that title as well, but I know Celta Vigo are very good. They are a very difficult team."