The Dutch hot shot's prowess had been questioned by the doubters in the early weeks of the new campaign after a stuttering start.
But his brilliant brace in the Champions League against last season's runners-up is a clear indication van Nistelrooy is rediscovering his sharpness.
Van Nistelrooy remained confident in his ability during his mini-drought and is delighted to have silenced the snipers.
"I have proved people were wrong to write me off," said van Nistelrooy.
"Strikers have difficult times but the secret is to look forward, not worry about what has happened in the past.
"I live believing the next moment will be yours and that things can very quickly change for you in football.
"To score two against Leverkusen was fantastic for me."
Van Nistelrooy's personal trough was symptomatic of the Red Devils' turbulent advent to the new campaign.
But after back-to-back Champions League successes and a Premiership triumph over Tottenham, the former PSV Eindhoven marksman believes the team may have turned the corner.
He added: "The team is looking good again. We are in a strong position in the Champions League and on a little run after winning our last three games.
"We have shown what we are capable of and the confidence has grown with each of those victories.
"The first half against Leverkusen was special and sent out a message about Manchester United."
Meanwhile, United's recent goalkeeping recruit Ricardo is prepared to bide his time before grasping his first team opportunity.
"I think all the keepers at the club will have opportunities this season because the campaign is so long and there are so many competitions," said the Spaniard.
"I just have to be patient and wait for the chance."
