The Dutch striker got Real's first goal in their 2-0 victory over Osasuna on Sunday; a result which gives the reigning champions a four-point lead over rivals Barcelona.
As the two sides prepare for El Clasico next weekend, van Nistelrooy believes that going into the game with the cushion will allow Real to express themselves safe in the knowledge that they will remain at the top of La Liga no matter what the outcome is.
No fear
"It was important to win (against Osasuna) so that we can go to the Nou Camp with a four-point advantage," he said.
"With this we can go there to attack, without fear. It will be a tough game and it is better to go secure in the knowledge that whatever happens we will remain leaders."
Casillas
Barcelona had closed the gap to a single point on Saturday with an impressive 3-0 win at Valencia. Samuel Eto'o continued his impressive return to the side with two goals, but Lionel Messi picked up a thigh injury which will rule him out for up to a month.
Real Madrid goalkeeper Iker Casillas feels that the loss of the Argentinean will be a major blow to the Catalan club, but that the returning Eto'o should help to soften the blow.
"The loss of Messi is very important for Barca because he's a key player in fantastic form, but they have Eto'o who has proven beyond doubt that he is well again," the Spanish international said.
Rijkaard
Barcelona coach Frank Rijkaard agrees with Casillas, and is confident that the return of the Cameroonian striker will help improve the club's chances of reclaiming the title.
"The victory against Valencia was very important psychologically," the Dutchman told Com Radio.
"Eto'o's quick touch and penetration created problems for Valencia. It's what we want, great goals and attitude. Now we have the chance for a good season."