The former Blancos striker lauded the Portuguese for breaking his Champions League goalscoring tally while taking to Twitter as part of Heineken's 'Share The Sofa' evening
The 37-year-old tweeted his thoughts on the game for Heineken throughout the encounter, as part of their '#ShareTheSofa' night, and praised Ronaldo for his maturity in leading Madrid through a tough start to the season.
Goal compiled a list of our favourite tweets from the Dutchman during and after the game, including his thoughts on Karim Benzema, Gareth Bale and the top four strikers in the world.
VAN NISTELROOY ON RONALDO'S INFLUENCE
"At the start of this season, Ronaldo has taken the team in his hands. You see that really happening now."
"Ronaldo keeps performing at his level because he's very committed, has a great internal drive."
"Ronaldo had a vision to be the best player in the world back then when he was 17 and he made that happen."
VAN NISTELROOY ON MADRID
"Benzema needs a goal in a game like today. The feeling that comes from it will lift him massively."
"Real Madrid are always one of the favourites, but this year they're not. Bayern is..."
"Bale will definitely deliver. They're building up to bring him after the winter break."
VAN NISTELROOY ANSWERS SUPPORTERS' QUESTIONS
Van Nistelrooy: "Definitely. You feel it around you on a daily basis. 20 pages of newspaper articles, constant TV coverage. There was definitely more pressure at Madrid than United."
VAN NISTELROOY'S VERDICT
"Would be a lucky win for Real tonight. Yellow card was lucky, but for the most part they've earned it."