The Red Devils will go into this weekend's encounter looking to improve on their worst start to a league season since 1989-90, while they are winless in four matches across all competitions.
United have also gone almost two months without a victory at Old Trafford, and Mourinho acknowledged that his side "need" to pick up all three points against the winless Magpies.
"[The match is] very important. We are in the beginning of October, and you look to tables all around Europe and, in many of the leagues, the tables don't reflect what is going to happen in a few months, or at the end of the season," Mourinho told reporters.
"We are in a position where we can do much better than that and to do that we need points – points that we lost, especially in the last two Premier League matches, with one point out of six. We know that to improve that position we need to win these three points.
"Only one defeat at home all season, only one defeat in the last seven matches, but not victories at home in the past three matches. Three draws – not the feeling of the defeat but not the happiness of the victory. So yes, it is important for us to try and win this match on Saturday."
United, who already find themselves nine points behind Manchester City and Liverpool, have only gone five games without a win on one occasion since 1999.