"Two years ago, I scored four goals (with Manchester United) against Sparta Prague in the Champions League," Van Nistelrooy was quoted as saying by Real Madrid's website after Sunday's 4-1 win.

"But this time is unique because we had five chances and scored four of them, something which doesn't usually happen. This was incredible."

The Dutchman pounded Osasuna's net three times in the first period before sealing the classy triumph after the break.

Van Nistelrooy took his goal tally to eight, one behind top scorers Fredrik Kanoute of Sevilla and Gabriel Milito of Zaragoza and level with Ronaldinho.

He scored the four goals in as many attempts, ironically, against goalkeeper and former team mate Ricardo, who joined Osasuna from Manchester.

"After the game, I spoke with Ricardo. He is a great person and a friend of mine," he said. "But on the pitch, I have no friends."

Real's win moved them into third place in the table, just three points behind leaders and arch-rivals Barcelona.

Van Nistelrooy believes that regardless how marvelous the win over Osasuna was, it just worth three points.

"It counts as one victory, so we must work hard to win our next game and keep winning every weekend," he said.

"The Spanish League is very difficult. We should stay focused and keep a maximum respect to our rivals if we want to win the title."